Former Conservative minister Dominic Grieve has said he has never experienced a modern British politician who is so “elastic with truth” as Boris Johnson.
“I've never experienced a politician in modern British history who is so elastic with truth," Mr Grieve said.
He accused his former party leader of telling “whopping lies” against people when it suits him.
Mr Grieve also said he would not support Mr Corbyn in the election either, describing his “extreme socialist policies” as “ghastly”.
He promised to not do anything that could put the Labour leader into Downing Street if elected as an independent in Beaconsfield.
Mr Grieve, who has represented the seat in Buckinghamshire since 1997, had the Conservative whip withdrawn in September for rebelling against the Prime Minister’s Brexit deal with 20 other Tory MPs.
He will face newly-selected Conservative candidate Joy Morrissey, an Ealing councillor who unsuccessfully bid to become the Tory’s choice to take on Sadiq Khan in next year’s London mayoral election.
She said: “It is a tremendous honour to have the opportunity to represent the constituents of the beautiful constituency of Beaconsfield.
“I will be moving here with my young daughter and husband to become an active member of the local community, campaigning on local issues important to residents, always representing their views at Parliament.”