MPs have warned Sir Keir Starmer that he faces a “civil war” inside Labour if he tries to reverse Brexit in an attempt to secure his embattled leadership.

Labour MP Dan Carden told the Prime Minister not to rejoin a customs union.

Firing the warning at any potential leadership rivals, he added: “We hear suggestions that this is being seriously contemplated by some at the very top of the Government.

“Moreover, we hear that it appears to be the aim of people who now have designs on the PM’s job.

“Andy Burnham has declared how he wants to see us back in the EU in his lifetime, while Wes Streeting wants us to have a deeper trading relationship with Europe.”

A row erupted after Health Secretary Wes Streeting called for a “deeper trading relationship with the EU” – a move which was interpreted as both a call to rejoin the Customs Union and an attempt to gain the support of Europhile Labour MPs ahead of a leadership bid against the Prime Minister.

Manchester Mayor Andy Burnham, a leadership contender, has also stated that he hopes the UK will rejoin the EU in his lifetime.

Speaking to the Mail on Sunday (MoS), Mr Carden added: “The European Union (EU) is… a low-growth bloc with a declining share of global GDP. Joining a Customs Union would mean scrapping our post-Brexit trade deals with places that are the 21st-century growth centres, such as the US and India.

“Shifting closer to Brussels would mean giving up our hard-won national freedoms.

“I urge Sir Keir not to seek to tie the UK into a new customs union or any other such arrangement which may carry a disguised name but amount to the same thing.”

Labour MP Graham Stringer told how Sir Keir would face “a rebellion of scores of Labour MPs if he sought to take us back into any sort of Customs Union”.

He told the MoS that “it will lead to civil war inside Labour”. He added: “Starmer’s Parliamentary colleagues know they stood on a clear manifesto pledge to do no such thing.

“It would be especially difficult for Labour MPs in the so-called Red Wall to support such a flagrant manifesto breach, as many have Reform breathing down their necks. They would be committing electoral suicide.”

Keir Starmer Reeling as Labour Civil War Erupts Over Fresh Brexit Question

A renewed debate over Britain’s post-Brexit relationship with the European Union has exposed fresh divisions within the Labour Party, placing Prime Minister Sir Keir Starmer under renewed political pressure as MPs, party members and commentators argue over the government’s long-term strategy.

The latest disagreement centres on whether Labour should seek a significantly closer relationship with the European Union beyond the existing arrangements or continue to respect the political boundaries established following the UK’s departure from the bloc. While ministers have repeatedly ruled out rejoining the European Union, the single market and the customs union, recent calls from some Labour figures for deeper cooperation have reopened a sensitive debate that many believed had largely been settled.

The issue has quickly become one of the most closely watched topics in Westminster, with critics warning that mixed messages risk confusing voters while supporters argue that Britain’s economic interests require a more pragmatic approach to relations with European neighbours.

Senior government figures have insisted that Labour remains committed to making Brexit work rather than attempting to reverse it. They argue that improving trade, strengthening security cooperation and reducing unnecessary barriers for businesses can all be achieved without revisiting the 2016 referendum result.

However, not everyone within the party shares the same view about how far those efforts should go.

Several MPs from different wings of Labour have publicly suggested that Britain should explore more ambitious agreements with Brussels if they would boost economic growth, ease trade friction and improve opportunities for businesses, universities and young people. Others remain cautious, warning that any proposal perceived as reopening the Brexit debate could alienate voters who supported leaving the European Union.

Those differing opinions have fuelled speculation about an emerging fault line inside the governing party.

Political analysts note that Brexit remains one of the most complex issues in British politics despite years having passed since the UK formally left the European Union. Although public attention has shifted toward inflation, healthcare, housing and the economy, questions about Britain’s relationship with Europe continue to influence trade policy, immigration rules, scientific cooperation and foreign affairs.

For Starmer, the challenge lies in maintaining party unity while appealing to a broad coalition of voters whose views on Brexit remain deeply divided.

Supporters of the Prime Minister argue that his current position reflects political reality. They say the country has little appetite for another prolonged constitutional argument and instead wants the government to focus on improving public services, supporting economic growth and reducing the cost of living.

According to this view, rebuilding practical cooperation with European partners—without reopening the membership question—offers the most realistic path forward.

Critics inside Labour, however, believe the government should be more ambitious.

Some argue that closer regulatory alignment in selected industries could help exporters by reducing paperwork and administrative costs. Others believe expanded agreements on scientific research, higher education and professional qualifications would strengthen Britain’s international competitiveness.

There are also voices urging ministers to negotiate wider mobility arrangements for students, researchers and skilled workers where mutual benefits can be demonstrated.

Not everyone agrees.

A number of Labour MPs representing constituencies that voted strongly in favour of Brexit remain wary of proposals that could be interpreted as reversing previous political commitments. They argue that trust with voters depends upon respecting earlier promises while demonstrating that the government can deliver practical improvements within the existing constitutional framework.

The disagreement has prompted renewed discussion among political commentators about Labour’s internal balance between its progressive urban support base and voters in towns and regions that played a decisive role in the Brexit referendum.

Conservative politicians have also seized upon the debate, accusing Labour of sending inconsistent signals over Britain’s future relationship with the European Union. Government ministers reject those accusations, insisting that their policy remains unchanged and that discussions are focused solely on improving cooperation where it serves the national interest.

Business organisations have generally welcomed efforts to reduce barriers affecting exporters, particularly smaller companies that face additional administrative requirements when trading internationally. Many industry groups argue that smoother trading arrangements could improve productivity without requiring fundamental constitutional changes.

Economists remain divided over the likely impact of any future agreement.

Some believe closer cooperation could gradually reduce costs for businesses, encourage investment and improve supply chains. Others argue that broader economic performance will depend far more on domestic policies involving taxation, infrastructure, workforce skills and innovation than on incremental adjustments to UK-EU arrangements alone.

Within Parliament, attention has increasingly turned to whether the latest disagreement represents a routine policy debate or something more significant.

Political scientists point out that governing parties frequently experience disagreements over major strategic questions. Differences of opinion do not necessarily indicate a leadership crisis, particularly when ministers continue to support the Prime Minister publicly.

Nevertheless, sustained public disagreement can create perceptions of instability, especially when opposition parties and the media focus on competing messages from different parts of the governing party.

For Starmer, maintaining discipline while allowing legitimate debate presents a delicate balancing act.

The Prime Minister has consistently argued that Britain’s future depends upon stable economic management, stronger international partnerships and practical solutions rather than ideological disputes. His supporters believe that approach reflects the priorities of many voters, who are increasingly concerned about living standards, healthcare and public services rather than revisiting arguments from previous years.

Others contend that Brexit policy cannot be separated from those wider economic questions.

Trade, investment, research funding, manufacturing supply chains and labour mobility all intersect with Britain’s international relationships, meaning discussions about Europe are likely to remain politically important for years to come.

As speculation continues, Labour MPs are expected to face increasing questions from constituents about how the government intends to reshape Britain’s place in Europe while honouring commitments made during recent elections.

Whether the latest disagreement develops into a broader internal conflict may depend on how ministers explain future policy decisions and whether they can persuade different wings of the party that economic cooperation and constitutional certainty are compatible objectives.

For now, the government insists that its position has not changed. Yet the renewed debate demonstrates that Brexit continues to cast a long political shadow over Westminster, influencing discussions far beyond the formal process of leaving the European Union.

With Parliament expected to scrutinise future agreements closely and political opponents eager to highlight any apparent inconsistencies, the issue is unlikely to disappear from the national conversation anytime soon. Instead, it may become one of the defining tests of Labour’s ability to maintain unity while navigating one of the most enduring and politically sensitive questions in modern British politics.