The 15 British sailors and marines seized by Iran in the Gulf last month said yesterday they were blindfolded, bound, kept in isolation and warned that they faced up to seven years in jail.

"Throughout our ordeal, we faced constant psychological pressure," they said in a joint statement.

"We were interrogated most nights and given two options. If we admitted that we had strayed, we would be back on a plane to the UK pretty soon. If we didn't, we faced up to seven years in prison," they revealed.

They heard weapons being cocked behind them and feared the worst.

The sole woman among the group, Faye Turney, was kept isolated for several days and told by her captors that the others had been freed and gone home.

The sailors and marines were released in Tehran on Thursday after a tense 13-day stand off and flown back to Britain for an emotional reunion with their families.

The sailors' description of their captivity was in sharp contrast to the images of them smiling on Iranian television. Those images were an Iranian "media stunt", they said yesterday.

After their arrest in the Gulf, the sailors and marines were taken to a prison in Tehran. "We were blindfolded, our hands were bound, we were forced up against a wall," they said in their statement.

They were "stripped and dressed in pyjamas... we were kept in stone cells, approximately eight feet by six, sleeping on piles of blankets. All of us were kept in isolation."

They insisted they had been arrested in Iraqi waters and answered accusations that they should not have surrendered so readily.

"Had we resisted, there would have been a major fight, one which we could not have won, and with consequences that would have a major strategic impact," Captain Chris Air said.

"I can clearly state we were 1.7 nautical miles from Iranian waters," Lieutenant Felix Carman told the news conference.

Asked for the government's reaction, a Foreign Office spokesman said: "The words of the group speak for themselves and we will give them careful consideration."

Britain has suspended boarding operations in the Gulf and is reviewing rules of engagement in the area's waters amid disquiet over how easily the sailors were seized on March 23.

"As part of this ongoing review, the operational procedures and the rules of engagement that go with them will be reconsidered," navy chief Admiral Jonathon Band told BBC Radio.