Rasoul Movahedian spoke to permanent under secretary Peter Ricketts for 30 minutes following the crew's capture last Wednesday.

A Foreign Office spokesman said: "We need confirmation of where the five sailors are being held, consular access and the speedy release of these men."

The Kingdom Of Bahrain racing yacht, owned by Sail Bahrain, was stopped by the Iranian navy as it sailed from Bahrain to Dubai.

Oliver Smith, 31, from Southampton, Oliver Young, 21, from Saltash, near Plymouth, Sam Usher, 26, from Scarborough, North Yorkshire, Luke Porter, 21, from Weston-super-Mare, and Bahrain-based radio presenter David Bloomer, thought to be in his 60s, were on board.

Foreign Secretary David Miliband said there was "no confrontation or argument" in discussions with Iran and stressed the capture had "nothing to do with politics".

But he said there was a "high level of concern" about the sailors, whose location is unknown.

Esfandiar Rahim-Mashaie, Iranian president Mahmoud Ahmadinejad's head of staff, told the country's Fars news agency: "Judiciary will decide about the five ... naturally our measures will be hard and serious if we find out they had evil intentions."

The Foreign Office said it was investigating the reports.

Earlier, Mr Miliband spoke of his concern at the capture of five British sailors in Iranian waters but said their detention had "no link" with politics.

Mr Miliband said efforts were continuing to secure the release of the crew of the Kingdom Of Bahrain racing yacht, which was stopped by the Iranian navy last Wednesday as it sailed from Bahrain to Dubai.

Bahrain-based radio presenter David Bloomer, thought to be in his 60s, Oliver Smith, 31, Oliver Young, 21, Sam Usher, 26, and Luke Porter, 21, were on board.

During Commons questions, Mr Miliband said: "There's no link at all between the position of the yachtsmen and the Iranian nuclear file or other political issues that exist between Iran and the international political community.

"We very much look forward to the yachtsmen being released on a consular basis. As we understand it, they are being treated well, as we would expect in Iran."

Earlier, he told reporters there was a "high level of concern" surrounding the incident.

"There's obviously a high level of concern about the five young yachtsmen and their position," he said.

But he said the incident should be treated as a consular matter.

"There's certainly no suggestion of any malicious intent on the part of the five young people," he said.

Efforts to free the men were delayed by a public holiday in Iran but Mr Miliband said he remained hopeful their release could be secured quickly.

"Our contact with the Iranian authorities has been dealt with in an appropriate and professional way," he said.