Former European Union Brexit negotiator Michel Barnier told EU News that it is up to the United Kingdom to decide whether it would want to rejoin the bloc, but that Brussels has made its conditions clear.

His comments come ten years after the UK voted to leave the EU by 52% to 48%, and at a time when polling shows a clear majority of the British public, across party lines, views doing so as a mistake.

“Brexit decided by a sovereign vote 10 years ago is done, but the future is open, and the door is open,” Barnier, a prominent centre-right politician who was Prime Minister of France from September to December 2024, said on EU News’ programme 12 Minutes With.

He argued that the UK government and political parties know what the conditions for rejoining are, noting that it should be clear to London that it “cannot have its cake and eat it” when it comes to negotiating its future relationship with Brussels.

Barnier, who referred to Brexit as a lose-lose game, explained that it would, for example, be possible for the UK to join the single market — the bloc’s borderless economic area — without joining the EU, as Iceland, Liechtenstein, and Norway have done.

“But the conditions are very clear for any country joining the single market,” he said, adding that one of them would be “respecting the four freedoms” — free movement of goods, services, people and capital.

Becoming a full member of the single market, however, is currently seen as a non-starter.

Not joining the single market was a key “red line” for the Labour government under outgoing Prime Minister Keir Starmer. It was his way of sticking to his party’s pre-election manifesto pledges in a bid to appease Leave voters while navigating a “reset” with the EU.

Instead, Starmer’s approach was to take the UK further into the market in some sectors. However, this partial or “à la carte” arrangement has historically not been on the table for the EU. Barnier echoed that the UK should not be allowed to cherry-pick from EU policies.

It is unclear where Andy Burnham, who is currently an MP and the most likely candidate to replace Starmer in Number 10 following his resignation on Monday, stands on the matter.

Liberal Democrats and pro-EU Labour MPs have already urged him to “drop the red lines” on the single market and customs union, which Brussels sees as a key snag in the rapprochement efforts.

Rapid re-entry is possible

Barnier hinted at a possible fast-tracked process for the UK if the remaining alignment on regulation continues, eluding the long, complex, multi-phase accession process faced by candidate countries such as Ukraine, Moldova and Western Balkan states.

“The answer [to how long the process will take] is in the hands of the UK,” he said. “If from now to the time of new negotiations starting, the UK creates a huge divergence from the standards, the norms for food, for security, we will have a problem, and it will take time, much more time.”

He noted that, “if there is no divergence, no crucial divergence, it will be very rapid,” adding, “We can’t compare the very long process for new countries that want to access the EU and former member states.”

In the meantime, Barnier said, Brussels and London can work together on many fronts.

“We have a lot to do together, for instance, for defence, for security, for cooperation between the services, even for investment in artificial intelligence or new technologies that we are seeing,” he said.

He proposed to facilitate this type of cooperation between the UK and the EU through the creation of a new body, referring to “a kind of European Council for Defence and Security”, which would sit “alongside the current institutions”.

“This would be open to some countries that are no longer or not yet in the EU, for instance, obviously the UK, but also Norway or Ukraine.”

The UK and EU are in the midst of “reset talks” and were hoping to conclude talks on an agrifood agreement (slashing barriers by aligning sanitary and phytosanitary rules), an emissions trading deal, and a youth mobility scheme (granting special visas to young Europeans and Britons) at a summit on 22 July.

However, European Council President António Costa confirmed earlier this week that the meeting, for which a date was set only last week at the G7 summit in France, would be postponed in light of Starmer’s resignation.