By John Geddie

LONDON (Reuters) - Negotiations over Britain's departure from the European Union are very complex and are going to take longer than the scheduled two years, Eurogroup President Jeroen Dijsselbloem said on Wednesday.

Britain has said it will trigger Article 50 of the Lisbon Treaty by the end of March next year, starting a 24-month countdown to its departure from the bloc.

But with the British government's stance toward Brexit starting to show signs of splintering, and Europe eager to pull together and prevent a populist backlash that could fracture the EU further, talks are likely to be strained and drawn out.

"Negotiations are hugely complex... They are going to take a lot longer than two years," Dijsselbloem, the Dutch head of the group of euro zone finance ministers, said at an event in London.

"Since the outcome of the British referendum, the UK and the continent are regarding each other with some suspicion ... It is a lose-lose situation which we can only manage as well as possible."

A leaked memo published by British media this week said that the UK government has no overall strategy for leaving the European Union and splits in Prime Minister Theresa May's cabinet could delay a clear negotiating position for six months. The government dismissed the memo as having no credibility.

Dijsselbloem said many in Europe were also unprepared for Britain's vote in June to leave the bloc, which was not predicted by pollsters.

"People make jokes about the UK not having a Brexit plan, but many Europeans didn't have a plan either," said Dijsselbloem.

He said his "preferred" option would be for Britain not to trigger Article 50, but if this was not possible he would want to maintain as much free trade between his home country, the Netherlands, and the UK as possible.

Immigration, a major driver behind Britain's vote to leave the EU, has also been driving Dutch voters toward the far-right party of populist Geert Wilders ahead of elections in the Netherlands next year.

Wilders, who is campaigning on a platform that would have the Netherlands close its borders to Muslim immigrants and quit the euro and European Union, is polling higher than Prime Minister Mark Rutte's conservative VVD Party and Dijsselbloem's Labour party.

But Dijsselbloem said Dutch law would not currently allow for a referendum on EU membership similar to Britain's and that the people wouldn't want it anyway.

"The Netherlands will stay in the EU, the public support (for the EU) has increased dramatically after Brexit," he said.

(Reporting by John Geddie; Editing by Jeremy Gaunt and Andrew Heavens)