The former Medway Labour MP Bob Marshall-Andrews has defected to the Lib Dems in a blow to his former party.

The barrister, who represented the Medway constituency from 1997 to 2010, denounced the “abject failure of the Labour leadership” following the Brexit referendum.

His switch will prove a major fillip for the Lib Dems, who are likely to target the nearby Kent seat of Maidstone and the Weald in the campaign.

Mr Marshall-Andrews said his former party’s flimsy Brexit arguments and inability to get their views across to voters had “provided a concession of both votes and credibility to Ukip”.

He added: “At present there is manifestly a huge vacuum on the centre-left represented in substantial part by the 48 per cent of the electorate who rejected Brexit and the lies on which it was based.

“To many, including me, there was a forlorn hope that a reformed and radical Labour Party would rise to historic occasion. It has not and shows no real sign of doing so.”

Mr Marshall-Andrews had been a long-standing member of Labour, joining the party in 1971.

He also said the party should have chosen not to field anyone in the Richmond Park by-election, caused when Zac Goldsmith stood down after the third runway decision. Sarah Olney, the Liberal Democrat, took the seat.

He said he left Labour with a “heavy heart”, but added that the Liberal Democrats offered “some radical hope”.

The party's leader Tim Farron said: "Bob, like many progressive Labour people, is coming over to the only party that is offering a credible opposition to a divisive Tory Brexit government."

He was a persistent critic of Tony Blair’s administration and famously declared he had lost his Medway seat in the 2005 election, saying that the Iraq war had cost him his job - only for there to be a recount which delivered him a narrow victory.