The European Commission President Jean-Claude Juncker has said the UK needs to 'get its act together' over Brexit.
His comments come ahead of a key vote by British MPs on the withdrawal agreement.
Mr Juncker insists the European Union is not trying to keep Britain in the bloc, and wants to start discussing the future relationship as soon as possible.
"All we want is clarity about our future relations. And we respect the result of the referendum", he told German newspaper Welt am Sonntag.
He said the UK needs to 'get its act together' and also accused some British people of being unreasonable for expecting Brussels to put forward a solution.
He said: "I find it entirely unreasonable for parts of the British public to believe that it is for the EU alone to propose a solution for all future British problems.
"My appeal is this: get your act together and then tell us what it is you want. Our proposed solutions have been on the table for months."
British Prime Minister Theresa May in Brussels
On Britain's future relationship with the EU, with particular regard to Northern Ireland, he said: "It is not us who are leaving the United Kingdom - it is the United Kingdom that is leaving the European Union."
Asked if he saw any chance of a second Brexit referendum, Mr Juncker said: "That is for the British to decide."
The comments come as a senior British cabinet minister said the chances of the UK leaving the EU are 50-50 if MPs reject the withdrawal deal.
International Trade Minister Liam Fox believes Brexit is only guaranteed if there is support in the House of Commons for the agreement.
He told Britain's Sunday Times that rejecting the deal would be "incendiary" and that MPs there must support it as "a matter of honour".
"Parliament cannot now, with any honour, renege on that result [of the referendum]," he said.
"Were they to do so, I think you would shatter the bond of trust between the electorate and parliament. And I think that would put us into unprecedented territory with unknowable consequences."
The vote, which was delayed last month, is now due to take place in the second week of January.
