The 48-year-old presenter came out with a string of cheeky comments while sitting in for Terry Wogan on the station's flagship show on Friday morning.

They included calling colleague Ken Bruce an "old fool" and referring to the presenter of the Pause For Thought slot as "an old prune".

She has apologised to listeners - and blamed it on a lack of sleep.

"I has some disturbing news last Thursday night which affected my sleep pattern and consequently energy levels," she said.

"I'm feeling fine now, but I'm going to take a week off for a bit of a rest and it will be business as usual next Tuesday."

A spokesman for Radio 2 said: "She asked to have a week off to get some rest, and we said yes."

Ken Bruce is to fill in for her for the rest of the week.

Sarah Kennedy, who first joined Radio 2 in 1976, is known for her racy sense of humour on her shows, even championing a series of songs about underwear.