The Brussels bureaucrat said he will step down just after the Brexit deadline on March 29, 2019 – prior to the end of the two-year transition period proposed to allow EU-UK trade talks to continue.
Not always seen as a friend of Britain’s, he admitted the future trade relationship between the UK and the EU was the “most important” factor in the negotiations, but said an agreement could take years.
Mr Barnier revealed he would oversee talks until the end of European Commission president Jean-Claude Juncker’s term ends in 2019, which will not include the transition period the EU appears to be encouraging.
He told German newspaper, Handelsblatt: “After that, I will see where I can still make myself useful in the EU.”
The Frenchman has been tipped to replace Mr Juncker if he secures a successful Brexit in the eyes of the bloc.
Speaking yesterday, he warned negotiations would continue to be “difficult”.
He told Les Echoes: “The two phases are difficult. The second will be very different and will last several years.
“It is truly unique because instead of promoting regulatory convergence, it will aim to frame a difference.
“It will involve risks, including about its political ratification, making all the more necessary transparency around these topics.”
He admitted an agreement on a time-limited transition period after Britain leaves the bloc in March 2019 is possible.
Mr Barnier added: ”If we reach an agreement on the orderly withdrawal of the United Kingdom, such a period, both short and framed, is possible.
“To my mind, it makes sense that it covers the financial period, so until 2020.
“It would leave us more time to prepare for the future relationship.”
His comments come after Theresa May told MPs there could be no transition period after Britain leaves the EU without an agreement on a trade deal.
In a Commons statement, the Prime Minister said she remained confident a deal was possible following last week’s EU summit in Brussels.
Opposition MPs raised concerns, warning Britain was heading for a “cliff-edge” split from the EU which businesses are desperate to avoid.
On Friday leaders of the remaining 27 EU member states agreed to prepare for trade talks with the UK by Christmas.
In the Commons, Mrs May said it was not possible to have a transition unless they knew what they were transitioning to.
She said: “The point of the implementation period is to put in place the practical changes necessary to move to the future partnership.”
“In order to have that you need to know what the future partnership is going to be.”