Sir Keir Starmer has promised that Labour will seek to renegotiate  Britain’s relationship with the European Union if they form the next government. 

The vow was made during an interview with the Financial Times, ahead of a meeting with French President Emmanuel Macron later this week.

However, the commitment to pursue a significant rewrite of the U.K.-EU Trade and Cooperation Agreement (TCA) has been criticised by European experts.

The SNP said Sir Keir's promise to Make Brexit Work was "every bit as intellectually dishonest as 'Brexit means Brexit' and 'Oven Ready Deal'."

A Conservative spokesman described it as yet another Labour u-turn.

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The TCA negotiated by Boris Johnson is up for review in 2025.

Sir Keir told the paper: “Almost everyone recognises the deal Johnson struck is not a good deal – it’s far too thin.

“As we go into 2025 we will attempt to get a much better deal for the UK.”

The Labour leader said he was confident a better deal could be secured from Brussels. Sir Keir has repeatedly and explicitly ruled out rejoining the EU, promising that his party will "make Brexit work." 

“I do think we can have a closer trading relationship as well. That’s subject to further discussion,” he said.

“We have to make it work. That’s not a question of going back in. But I refuse to accept that we can’t make it work. I think about those future generations when I say that," he added.

“I say that as a dad. I’ve got a 15-year-old boy and a 12-year-old girl. I’m not going to let them grow up in a world where all I’ve got to say to them about their future is, it’s going to be worse than it might otherwise have been.

“I’ve got an utter determination to make this work.”

He cited security, innovation and research as areas where the UK and EU could move closer. 

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Wolfgang Münchau, the director of Eurointelligence described the plan to stay outside the single market and the customs union, and get a better deal as “a political lie.” 

“It will almost certainly be exposed as such,” he added. 

The EU expert said there was almost certainly not a better deal available to the UK. 

“There was a lot of vindictive commentary from the EU during the entire Brexit process, but the deal that was eventually agreed was a reasonable third-country trade deal. 

“The two big remaining issues at the time have since been resolved: Northern Ireland and Britain's associate membership of the EU Horizon's science programme. 

“If your bottom line is that you do not wish to rejoin the single market and the customs union, there really is not a lot more out there.”

He said that if the EU played hardball with a Labour government, then it was likely pressure would grow from inside the party for another referendum. 

“The only way to do this would be the way David Cameron did this: put it in a manifesto and see whether you get a majority. Cameron did this in 2015, very much to everybody's surprise, including his own. 

“We would not bet on history repeating itself in the reverse direction. Getting back in is a harder job than getting out. 

“At the very least, you would need somebody who knows what they are doing."

Alyn Smith, the SNP's Europe and EU Accession spokesperson said 

"Yet again, Labour let Scotland down and prove independence in Europe is our best option.

“'Making Brexit work' is every bit as intellectually dishonest as 'Brexit means Brexit' and 'Oven Ready Deal'. It is a tragedy for Labour to have so enthusiastically followed the Tories down this rabbit hole.

"The reality is 'Out Means Out.' You can't be out of a club and expect any goodies.

"The EU Commission has already said that the review of the TCA will be about housekeeping, not major change. There is zero appetite in Brussels for cherry-picking on any great scale.

"There are improvements that could be made, especially on things like opting back into ERASMUS student exchanges, visas for touring creatives and a comprehensive phytosanitary deal to ease border checks on agricultural goods, but unless Labour commits to rejoining the Single Market and Customs Union then there's only so far they can go."

A Tory spokesman said: "Three years ago he promised he wouldn't seek major changes to the UK's new relationship with the EU, but now his latest short term position is that he will.

"What price would Keir Starmer be prepared to pay to the EU for renegotiating our relationship?"