Serious negotiations on Britain's exit from the European Union cannot begin until the end of next year, a former senior EU official has warned.
Herman van Rompuy, the former president of the European Council, said discussions on the "hard core" issues would have to wait until after elections in France and Germany in May and September.
"Before the German elections and before there is a new German government, no serious negotiations will take place," he told the BBC Radio 4 Today programme.
"You can always start with more technical matters but the hard core - the difficult topics - will be tackled after the constitution of the new German government. That will be October-November."
Mr van Rompuy said that while there was no desire to "punish" Britain for voting to leave, the UK had "not many friends" among the other 27 member states and the negotiation would be "difficult".
He warned that maintaining free movement of labour would be a "red line" if Britain wanted to remain part of the single market - pointing out that it formed part of the EU's agreements with Norway and Switzerland.
"Any negotiation will be a difficult negotiation," he said.
"Of course we want an agreement that represents some sort of mutual benefit. There are huge economic interests but there are also red lines. It is very well known that freedom of movement is one of those red lines.
"It is very difficult for the European Union to do something else vis a vis Britain compared to what we agreed upon with Norway and Switzerland.
"The big question is, even if there is some room for manoeuvre, is this sufficient for the British negotiators? It needs two to tango."
Mr van Rompuy said the Brexit vote was seen in the EU as a "political amputation of the first degree" and leaders would be keen to avoid further breakaways by member states.
"There is not a feeling that we have to punish, but on the other hand most leaders don't want to encourage other exits," he said.
"Britain had not many friends any more. I saw this clearly when I was in office when we had to vote on candidacy of Jean-Claude Juncker for the presidency of the commission. Britain was isolated.
"We consider the Brexit a political amputation of the first degree. That image of a strong Europe, that is tarnished a lot after Brexit."