By Michelle Martin

BERLIN (Reuters) - Scotland's Brexit negotiator said on Thursday it was still frustratingly unclear what kind of divorce the British government was seeking from the European Union, nearly five months after Britons voted in a referendum to leave.

"We're not clear on what they want, exactly how they want it - there is some considerable lack of clarity in the present situation," said Michael Russell, who is representing pro-EU Scotland in discussions about Brexit.

"It's been frustrating but we are entering into those negotiations with good faith and we presume they are too," he told Reuters during a visit to Berlin. Despite the uncertainty, Scotland would continue to work with the British government, he said.

While 52 percent of Britons voted to quit the EU in the June 23 referendum, a 62 percent majority in Scotland voted to stay in the bloc, putting a strain on the centuries-old union between London and Edinburgh. That has raised the possibility that Scots might press for a new referendum on independence, even though more than 55 percent voted in 2014 to stay in the UK.

A leaked memo this week from consultants Deloitte said Britain has no overall strategy for leaving the EU and splits in Prime Minister Theresa May's cabinet could delay a clear negotiating position for six months. The government dismissed it as having no credibility

Russell, a member of the pro-independence Scottish National Party, has previously suggested Scotland could be allowed to run a separate immigration policy from the rest of the UK to accommodate its different economic and demographic needs within a new constitutional set-up.

Asked how this could work, he said there were various models elsewhere, including Canada, but declined to say which, if any, was the favored option.

A deal was feasible if people accepted the principle, Russell said. "I think everything is doable in those circumstances and that's the message we're getting from the other EU members."

Britain intends to formally launch the separation process by the end of March, initiating a two-year negotiating period with the rest of the EU in which a central issue will be access to its tariff-free single market.

Failure to reach a deal could lead to a situation where tariff barriers spring up, defaulting to levels set by the World Trade Organization. Russell said that was not a sensible option, and sectors like agriculture could emerge as "big losers".

(Additional reporting by Joseph Nasr; Writing by Michelle Martin; Editing by Mark Trevelyan)