Charles Kennedy has warned his supporters that they must now build on their electoral success.

Arriving back at the Liberal Democrat's headquarters in Cowley Street on Friday, a buoyant Kennedy told well-wishers "the really hard work starts now".

"We have moved ourselves up a league," the Lib Dem leader said. "That means the level of scrutiny we receive is going to be that bit more stringent. I welcome that."

Kennedy gave his assessment of Thursday's results. "We completely laid to rest the talk of four years ago that it was a one-off event," he said. "It shows that we can take from both - and we can win from both again."

Kennedy said that the low turn-out and the triumph of the BNP in Oldham were both causes for concern.

The party's other achievement of election night, Kennedy claimed, was that more women MPs were joining the Lib Dem ranks - the only political party to increase its share of female backbenchers.

With reference to the media predictions that he would not survive his first election as party leader, Kennedy asked party workers "did I pass the audition?"

His predecessor, Sir Paddy Ashdown, paid Kennedy a warm tribute and revealed that he had an added reason to be cheerful.

"The result, in one word, is brilliant. I said that we would get 20 per cent and around 52 seats. In fact I was so confident that for the first time I put a bet on the result," he said.