Sir Keir Starmer has promised to try to get a “much better” Brexit deal for the UK if he wins the general election expected next year.

But although the leader of the UK’s opposition Labour party described the deal negotiated by then prime minister Boris Johnson in 2020 as “far too thin”, he has ruled out forming a customs union with the EU and seeking membership of the single market.

What could the Labour leader achieve within the Brexit “red lines” that he has set himself?

When could Starmer negotiate a reset?

Starmer’s advisers believe that his election would create a diplomatic inflection point that could allow him to draw a line under eight years of often bruising negotiations between London and Brussels under successive Conservative governments.

Prime Minister Rishi Sunak has already improved relations with the EU, concluding his Windsor framework deal to break the diplomatic deadlock over post-Brexit trading arrangements for Northern Ireland and taking up membership of the Horizon Europe science exchange programme.

Starmer could look to build on this limited progress via the five-yearly “implementation review” of the UK-EU Trade and Cooperation Agreement, which can begin from the start of 2026.

Can the UK get the EU to improve the TCA?

Trade and diplomacy experts warn that while the UK is fretting about the fallout of the TCA for its exporters, in most European capitals Brexit is yesterday’s problem. Senior EU officials say the bloc is now focused on issues such as immigration, net zero, energy security and plans for Ukraine to become a member state.

“There’s little appetite to reopen the Brexit psychodrama in Brussels,” said one, ahead of Starmer’s trip to Paris this week to meet French president Emmanuel Macron, which has been touted as laying the early groundwork for a reset.

Charles Grant, the director of the Centre for European Reform think-tank, warned that the EU side had “many other priorities” and any initiative from a Labour government would require careful framing and a clear “offer”.

“Before he takes office Starmer needs to work out what he wants to change in the Brexit settlement, and then forewarn EU leaders of what they should expect from Labour,” he added.

What can the UK offer to the EU?

The UK side will have to think carefully about a quid pro quo to unlock more flexibility from the European Commission on trade issues. This could include paying into EU programmes, like the Erasmus student exchange scheme that Johnson quit, or easier work visas for Europe’s young people and students.

Other potential areas for deeper co-operation include diplomacy and security. The UK could join the bloc’s schemes for financing military aid to Ukraine or sign a defence pact enabling London to contribute advisers to EU peacekeeping missions abroad — such as Operation Althea, which oversees the peace agreement in Bosnia and Herzegovina. Deeper cyber security and intelligence co-operation is another area that would be of value, especially to eastern and Nordic EU states.

Around renewables, London could look to build on an agreement signed last April to work together on renewable energy via the North Seas Energy Cooperation, a regional offshore grid co-chaired by the European Commission.

Linking UK carbon-pricing systems with those of the EU would also reduce frictions caused by forthcoming carbon border taxes. London could also offer to share its disused North Sea oilfields for carbon capture and storage, a geological asset unique to the UK.

Can the TCA be improved within Starmer’s red lines?

By ruling out single market membership and a customs union with the EU, trade experts say Starmer has significantly limited how far the UK’s post-Brexit trading relationship with the bloc can be improved.

They also warn that negotiations with Brussels are likely to be protracted and slow, with no sense of urgency on the EU side — unlike in 2019 or 2020 when both sides were trying to avoid a “no deal” Brexit.

The UK could try to negotiate some improvements for individual sectors of the economy — such as a veterinary agreement to reduce checks on animal and plant products, which would benefit food and drink exporters.

Aligning with EU rules will cut red tape and reduce border costs for individual sectors, but would entail the UK following large amounts of regulation without having a say over their creation, risking a political backlash at home.

To ease so-called rules of origin issues, which require products to be about 50 per cent UK-made in order to enter the EU tariff-free, London could seek to join the Pan-Euro-Mediterranean (PEM) Convention, making it easier for British companies with supply chains running through countries such as Turkey, Israel, Morocco and Switzerland to export tariff-free to the EU.

But Sam Lowe, trade expert at Flint Global, warned this would cut across existing elements of the TCA and would not address some areas of friction, such as the stand-off between the EU and UK over electric vehicles.

Labour has pledged to seek “mutual recognition agreements” for professional qualifications, which Brussels has done with other trade partners, but experts warn that this will take time. It took Canada nine rounds of negotiations and more than a year to secure a single deal on architects.

David Henig, a former official at the UK Department for International Trade who is now at the European Centre for International Political Economy think-tank, said such negotiations “won’t be automatic or easy”. “The EU will want to make sure the UK is committed to regulatory alignment, and I suspect may only want to start with a couple of sectors,” he added.

London could also take unilateral steps to reduce frictions for business, as it has already by partially recognising the EU “CE” standards mark. It could also speed up its programme to digitise border arrangements. 

Can Starmer really fix Brexit?

Given Starmer’s self-imposed red lines on rejoining the single market and a customs union, there are clear limits to how far any future negotiation can remove the barriers to trade erected by the TCA.

Some experts warn that the Labour leader’s aspirations will quickly get bogged down in negotiations in Brussels while attracting domestic political flak from Conservatives accusing him of “betraying Brexit” and turning the UK into a rule taker from Brussels.

Others are more optimistic, pointing out that Starmer can present himself as a clean break from the Conservative years. Analysts add that by gearing up to admit Ukraine, Brussels may have to build more flexible arrangements for non-members in the future.

Mujtaba Rahman, head of European analysis at the Eurasia Group think-tank, argued that with the right political leadership there could be more space for innovation on the EU side, particularly since Brexit has not tempted other states to seek to leave the bloc.

“If Starmer delivers consistent British engagement with the EU, based more on shared values and less on domestic politics, that will create goodwill, which will then underpin the dynamic between the two sides across the board,” he said.