HMS Cumberland has been ordered to stay on stand-by in the Mediterranean because of the crisis in Libya.
The Type 22 frigate was due to begin sailing back to Britain after a six-month deployment east of Suez conducting anti-piracy patrols and protecting oil platforms.
But she has been ordered to stay in the Mediterranean while the government decides how to get Britons home from Libya.
The country has been engulfed in political turmoil in the wake of the revolutions in Tunisia and Egypt.
HMS Iron Duke is currently on patrol in the Gulf but the Ministry of Defence said there are currently no plans to divert her duties to Libya.
The situation in Libya took an apparent turn for the worse this afternoon when the country’s leader Col Muammar Gaddafi refused to stand down despite widespread anti-government protests.
In a speech to the nation, he said he would not leave the country and would ‘die a martyr.’
More than 300 people are believed to have died since protests began last week.
Foreign Secretary William Hague said the safety of British nationals in Libya is of ‘paramount concern’.
He said: ‘We are shocked and appalled by the levels of violence unleashed by the Libyan government in recent days. The situation in Libya is worsening and remains highly unpredictable.
‘The Royal Navy Frigate HMS Cumberland is being redeployed from the Eastern Mediterranean to international waters near Libya so that it is pre-positioned in case it is required to play a role in assisting British Nationals, if needed.’
Mr Hague also said his department is making arrangements for a charter plane to travel to Libya in the next 48 hours and is working with airlines in other countries to get as many British nationals out of Libya as possible.
It is not the first time a navy ship has been deployed to assist in the evacuation of British nationals from a crisis zone.
In 2006, the Royal Navy successfully assisted in the evacuation of British Nationals from Lebanon.
‘As you would expect, UK forces are fully trained and prepare for this kind of event,’ said a Royal Navy spokesman.
Cumberland, which is based in Devonport, has 250 sailors on board.
The frigate, which was commissioned in 1989, is one of four axed in the government’s Strategic Defence and Security Review in October last year. She is due to leave service in April this year.