Sir Keir Starmer has hinted at a potential new phase in the Brexit saga, expressing his willingness to bring the UK into closer alignment with the European Union, particularly with the single market, if it serves the UK’s “national interest.”

In some of his most assertive remarks since the referendum, Starmer suggested that, under a Labour government, he might consider reinstating a system that was abandoned when the UK exited the EU in 2019.

Such a decision could ignite significant political controversy, especially at a time when migration figures are approaching record levels.

This shift would also contradict a commitment from the 2024 election manifesto, where he promised there would be “no return” to the previous system.

The single market operates on the principle of unrestricted movement of goods, services, capital, and people. The latter concept was a central argument for the Leave campaign advocates a decade ago.

During a BBC interview, Starmer emphasized that there would be no return to the full free movement policy, aside from a youth mobility scheme. This program would permit thousands of citizens under 35 from both the EU and the UK to work and travel freely.

But the EU is certain to make wider free movement of people part of any negotiations around single market access.

Sir Keir told the BBC’s Sunday With Laura Kuenssberg : ‘I think we should get closer, and if it’s in our national interest to have even closer alignment with the single market, then we should consider that, we should go that far.

‘We’re already aligning on energy, reconnecting to energy in Europe on emissions, but I think the single market further alignment, as I say, if it’s in our interest to do so, we should take that step.’

But he appeared to pour cold water on suggestions the UK should re-join a customs union with the bloc after his Health Secretary Wes Streeting said the arrangement had ‘enormous economic benefits’. 

In some of his strongest comments yet about Britain’s post-Brexit relationship with Brussels under Labour the Prime Minister said he would look at rules governing border checks.

Speaking to the BBCSir Keir insisted there would be no return to free movement beyond a ‘youth mobility scheme allowing thousands of EU and UK citizens aged under 35 to work and travel freely.

Asked whether he would be willing to revisit freedom of movement, allowing EU citizens with no limit to come to the UK, he said: ‘No, but we are looking at a youth mobility scheme which will be for young people to travel, to work, to enjoy themselves in different European countries, to have that experience.’

He also lashed out at ‘the falsehoods peddled by Nigel Farage and others’ during the Brexit referendum in 2016 and insisted his Government was ‘quietly, seriously getting on with diplomacy’ instead of ‘the politics of melodrama’.

It came as he was warned he he faces a ‘civil war’ inside Labour if he tries to reverse Brexit in an attempt to shore up his embattled leadership.

The 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.

Mr Streeting’s potential main rival in any contest, Manchester Mayor Andy Burnham, has also been agitating against Brexit, saying that he hopes that the UK will rejoin the EU in his lifetime.

Tory leader Kemi Badenoch has told Labour not to try to boost its flagging poll ratings by ‘re-opening old Brexit wounds’.

Now Labour MP Dan Carden has warned Sir Keir – and those seeking to succeed him – not to rejoin a Customs Union, saying: ‘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.’

Mr Carden’s reference to the mayor comes after Westminster sources revealed his Liverpool Walton seat was on the list of constituencies which Mr Burnham had targeted in the hope that the sitting MP would stand aside to allow him to fight a by-election, return to the Commons and then challenge the Prime Minister.

Prime Minister Sir Keir Starmer (left) speaks to European Commission President Ursula von der Leyen (rigtht) during the UK-EU Summit at Lancaster House in London on May 19, 2025

Health Secretary Wes Streeting (pictured) called for a ‘deeper trading relationship with the EU’

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 MPs in the pro-Brexit ‘Red Wall’ seats of the Midlands and North are particularly concerned about the threat posed by Nigel Farage’s Reform UK, which would make political capital out of any Brexit backsliding by Labour.

Labour MP Graham Stringer said the PM 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 Mail on Sunday: ‘It will lead to civil war inside Labour. 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.’

Mr Streeting said in an interview last month that Britain should pursue closer economic ties with the EU. ‘The best way for us to get more growth into our economy is a deeper trading relationship with the EU,’ he said. ‘We’ve taken a massive economic hit leaving the European Union.’

Manchester Mayor Andy Burnham (pictured) has said that he hopes that the UK will rejoin the EU in his lifetime

Deputy Prime Minister David Lammy also claimed that countries such as Turkey were enjoying economic benefits from Customs Union membership.

Their remarks came after the Government faced claims it was watering down Brexit after announcing the UK would rejoin the Erasmus system of student exchanges in 2027, at a cost of £570million per year.

Ms Badenoch accused Labour of embarking on a desperate ploy to shore up its core vote and warned the move would mean Britain giving up the trade deals it has struck since leaving the EU, including with the US and India, while opening the door to more demands for concessions from Brussels.

She said: ‘The only people advocating for such a policy – and here I include the trade union bosses who have also proposed it – do not understand what a Customs Union actually is.

‘This is why the renewed chatter about dragging Britain back into the EU’s Customs Union should worry us all.

‘It is not a sign of pragmatism – it is a symptom of Labour’s weakness. Now that the Government is weak and has no plan or new ideas, it has re-opened old Brexit wounds in the vain hope that doing so will make it more popular. It won’t.’

Sir Keir has previously ruled out rejoining the Customs Union, describing it as a ‘red line’.

Another senior Labour MP said privately: ‘Remainiacs around Starmer may be pushing this but it would cause mayhem in the Labour Party.

‘It would mean British businesses having to take rules from Brussels without the UK Government having a say on them. It would be unacceptable.’