Labour said the inquiries came in while Mr Hague was addressing his party conference in Blackpool the previous day.

During the hour-long speech about 50 people joined or agreed to join Labour, according to party sources.

In his speech, Mr Hague branded Prime Minister Tony Blair a liar, a fraud and a snob.

A senior Labour Party source insisted the televised speech had prompted a marked improvement on the "handful" of membership inquiries normally expected on a Thursday afternoon.

"We had 30 people signed up on credit cards and 20 said they were going to join and asked for membership forms to be sent to them.

"The main thrust of what they were saying was that they were expressing concern about the shift to the right of the Tory Party. They were saying: 'God, this is revoltingly right-wing'."

Labour also said it expected to recruit up to 1,000 new members as a result of a party political broadcast on the eve of Mr Blair's own speech to the Labour Party conference in Bournemouth two weeks ago.

But the most recently published figures from the party showed a slump in overall membership.