A hoaxer sparked off a fruitless sea search costing thousands of pounds on Friday evening when they made a false Mayday call to Pembrokeshire coastguards.

The call was at least the fifth picked up by coastguards in west Wales in the previous fortnight, who have now issued a stern warning to "the person playing this game".

A Milford Haven coastguard spokesman said: "Beware - making hoax calls is a criminal offence and if you are found you may be prosecuted."

Friday's incident involved coastguard teams from Tenby, Manorbier and Laugharne and Tenby's new all-weather lifeboat the Hayden Miller, and the inshore craft, which were deployed on an extensive search.

The Haydn Miller carried out numerous sweeps of the areas between Lydstep Point and Ginst Point at the mouth of the River Taf, while harbourmasters in Tenby and Saundersfoot checked their vessels and CCTV and police checked their database of vehicle owners.

The search began after a 7.48pm call simply containing the word mayday' was heard by the radio operator in the coastguard operations room at Milford Haven. The message was picked up by the coastguard aerial at Monkstone Point.

The operation was discontinued at 10.30pm, and has been classed as a false alarm with malicious intent. The spokesman added: "Over the past couple of weeks, several incidents with the spoken word mayday' have occurred, with the word being heard on aerials sited at Gower, Tenby and Hartland. All have been hoaxes.

"Not only is this extremely irresponsible of the persons making these false calls, it is highly dangerous for those in genuine trouble, as life-saving resources could be deployed on a false alarm in a different area."