The Royal Navy has insisted it has a “world-class fleet” after a report claimed all seven of its attack submarines were out of action.

The service’s four Trafalgar​-class boats and the three newer Astute-class are not ready for missions with just one at sea, it has been claimed – and that submarine is on trials after maintenance.

The Sun reported that repairs and maintenance were keeping the craft from their patrols.

A Royal Navy spokesman said: “We don’t comment on specific submarine operations. Britain has a world-class fleet, the Royal Navy continues to meet all of its operational tasking, deploying globally on operations and protecting our national interests as Britain steps up around the world.”

Sources told The Sun the Trafalgars, the last of which was built in 1986, were “on their last legs”.

HMS Ambush, one of the newer Astute-class, made headlines last summer after it collided with a ship off the coast of Gibraltar and sustained damage to its outer hull. Its nuclear plant was not affected and no crew were injured.

The three Astute boats, of seven planned, cost nearly £4bn to build with construction delayed by more than four-and-a-half years and costs exceeding the original budget by more than 50 per cent.

In January Downing Street was accused of covering up a failed Trident missile test involving one of the UK’s Vanguard submarines. The missile was said to have veered off course and the Government refused to answer questions about it, before details were leaked to CNN in the US.