Cutbacks have left the UK without a single warship specifically tasked with protecting the country's shores for the past month, the Ministry of Defence has confirmed.
The Royal Navy normally provides a minimum coverage of a frigate or destroyer fulfilling the role of Fleet Ready Escort (FRE).
This task is for the ship to be at high readiness for an emergency, including a terrorist attack, in UK waters or abroad.
However pressures on the navy caused by cuts to its fleet in last year's strategic defence and strategy review (SDSR) as well as its commitments to the Nato mission to Libya, has left it unable to fill the role.
In the SDSR, the Government cut the number of frigates or destroyers in the navy's surface fleet from 24 to 19.
The last ship to undertake the FRE role was the Type 23 frigate HMS Portland which left the position on October 3 to take part in the Joint Warrior Nato exercise off Scotland.
A Royal Navy spokesman said: "Due to the successful deployment of Royal Navy units to the Libya campaign, it has been necessary to reprofile the commitments of some ships.
"Should a FRE activation be required, a Royal Navy ship would be allocated."
The spokesman explained that although there had not been a ship specifically tasked as an FRE, one of the vessels taking part in the Joint Warrior exercise could have been allocated within 24 hours' notice.
He added that the FRE would not necessarily be on patrol during its tasking but could be alongside in port at high readiness to sail.