The EU's former Brexit negotiator has warned Andy Burnham he will not be able to rejoin its single market "à la carte", after the prime minister said he wanted to explore closer economic ties with Europe.
Burnham has said rejoining the EU's internal market is among options he could pursue to reshape the UK's long-term relationship with the bloc.
Speaking to the BBC's Sunday With Laura Kuenssberg ahead of a summit in 10 days' time, Michel Barnier said EU members would insist such a move require the UK to readopt conditions including the free movement of people.
Echoing a line made famous during the years-long negotiations over the UK's exit deal, he said there could be no "cherry picking" of the conditions for participation.
Since becoming prime minister in July, Burnham has suggested he could commit Labour to pursuing a much closer future relationship with Europe, including asking to rejoin the organisation as a full member, though he has ruled out major changes before the next election.
Barnier - who led talks over the UK's exit between 2016 to 2021 and had a three-month spell as French prime minister in 2024 - said the "door is open" within Europe to the UK rejoining as an EU member.
But he insisted that any move to rejoin the single market - which seeks to ensure that goods can be freely traded within Europe - would require the UK to follow the same terms as other members.
He added that this included compliance with regulations designed to promote the circulation of goods, services, capital and people, referred to collectively within EU institutions as the four freedoms.
Warning against the idea of a "single market à la carte", he said: "I said very, very often during these negotiations, the Brexit, there is no cherry picking.
"There will be no possibility to have one freedom and not the other. The four freedoms are clearly the four conditions to be inside a single market".
He also predicted EU countries would reject recreating the British financial rebate, first negotiated in 1985, that lowered UK contributions towards the EU's annual budget.
The UK's decision to leave the bloc had created "a new situation", he added, meaning a new rebate would be "off the table".
Barnier also compared Reform leader Nigel Farage to French politician Marine Le Pen. He said: "We have our own Farage. It is Mrs Le Pen. The same populism, the same lies, the same false promises."
Asked by Kuenssberg to clarify what he was referring to with his accusation of lies, Barnier said "for instance, when Mr Farage and Mr Johnson promised the UK people to get back [£350] million per week, it was not true, it was not possible. It was a lie".
The Vote Leave campaign, of which Boris Johnson became a key figure, has been criticised previously for the slogan on the side of their campaign bus that said Britain sent £350m a week to the EU, adding: "Let's fund our NHS instead".
Johnson said in 2017 that "once we have settled our accounts, we will take back control of roughly £350m per week. It would be a fine thing as many of us have pointed out if a lot of that money went on the NHS".
Critics have said that the £350m per week was an approximate sum which represents a "gross contribution" and did not take into account the UK's £75m-a-week rebate, or the EU's investments in the UK.
Johnson has since defended the claim saying the £350m was based on the UK's gross contribution to the EU, and was in fact an underestimate as UK contributions were due to rise.
In his memoirs published in 2024, Johnson said EU money spent in the UK was not "democratically controlled by the British people", and "even if the net figure was only £175m, that was still a hell of a lot of money".
Farage, who led Leave UK and was not part of the Vote Leave campaign so not connected to the £350m claim, said: "It is the same old Barnier - arrogant, out of touch and a bully. He vindicates our decision to leave every time he opens his mouth."
