The former president of the European Commission has said he "made a mistake" in listening to David Cameron after being told not to interfere with the Brexit debate in the UK.
Jean-Claude Juncker said he "should not have listened" to the former British prime minister and "spoken out" on the issue.
It comes as a row deepened in the UK over political lobbying sparked by Mr Cameron's use of government contacts to lobby on behalf of Greensill Capital, a now insolvent financial services company, prompting a series of investigations into the matter.
Speaking to the i newspaper, Mr Juncker said that Mr Cameron told him not to conduct interviews with the British press.
He said: "I should not have listened to David Cameron.
"He told me not to interfere in the debate in the UK, not to come to London, not to do interviews with the British press."
The UK left the European Union on 31 January 2020, seven years after the referendum ordered by Mr Cameron in 2013.
The decision to leave - by 52% to 48% - left the EU in shock, and Mr Cameron resigned as prime minister shortly afterwards.
A deal was finally brokered between prime minister Boris Johnson and Mr Juncker's successor, Ursula von der Leyen, after years of sometimes hostile negotiations that were hindered by the coronavirus crisis.
Mr Juncker said: "I made a mistake because I did not defend the EU's point of view in the UK.
"They asked me to shut up, so I shut up. That is something I criticise myself for. I should have spoken out rather than stay silent."
