By Leigh Thomas

PRAGUE (Reuters) - Britain needs to decide who represents it so that its EU exit talks can take shape without delay, French Foreign Minister Jean-Marc Ayrault said on Monday ahead of post-Brexit solidarity talks with eastern European member states.

In an interview with Reuters, Ayrault also said it was "not automatic" that Britain could get Swiss-style access to the European Union's single market without the free movement of capital, labor, goods and services elements that go with it.

"Britain clearly needs to sort out the problem of who represents it ... from there we can work on an agenda and a calendar," Ayrault said as he headed to the Prague talks.

British Prime Minister David Cameron, who led the campaign to stay in the EU, has said he will resign after Britons voted last week 52-48 percent in favor of quitting.

However, he has refused to trigger Article 50 of the EU's Lisbon Treaty, which sets out the rules for such a withdrawal over a two year negotiating period, and will stay on for three months while his ruling Conservative Party elects a new leader.

That decision has added to the concerns of his European partners amid fears it will increase the uncertainty the referendum vote has sparked.

Brexit advocate Boris Johnson has said Britain can have access to Europe's single market, without signing up to the free movement elements.

Ayrault appeared to open the door to such a possibility but said it was not a given.

"There are countries with access to the market without free movement. It's the case with Switzerland. It's not automatic. There are a lot of subjects to discuss.... I think first we need to find out exactly what the British want."

If Britain signs up to deal similar to the ones agreed by Norway, Switzerland or Iceland it would have to accept making budget contributions and other concessions that might be unacceptable to Brexit voters.

'NO LEGITIMACY'

Johnson is seen as a likely successor to Cameron, but for Ayrault, it is important that Cameron himself triggers Article 50, even though the current British government feels it lacks the legitimacy to do that.

"To express a hope I'd say it's better if he (Cameron) does it. But (British Foreign Secretary) Philip Hammond called me on Friday to say we don't have the legitimacy," he said.

"There's a question mark over whether David Cameron will say that at the European Council tomorrow. Maybe he'll say it, maybe he won't. He could give some clarity to Europeans, that would be preferable. What's certain is that it will not be him who does the negotiating."

Ayrault made a last-minute decision to join German Foreign Minister Frank-Walter Steinmeier in Prague as guests at a regular meeting of Eastern European EU members on Monday in a bid for solidarity in the aftermath of the Brexit vote.

"We need to preserve the unity of the 27 (other member states), to have lots of discussions between us. There could be several ways of doing that. No-one should be deciding for others," he said.

(Reporting by Leigh Thomas; Writing by Andrew Callus; Editing by Brian Love and Anna Willard)