London: Margaret Thatcher's successor as prime minister has told voters not to back the Conservative party at Thursday's election, sparking a rebuke from Boris Johnson who dismissed the intervention as "very sad" and "wrong".

Describing the United Kingdom's departure from the European Union as "the worst foreign policy decision of my lifetime", Sir John Major endorsed three former Conservative MPs expelled from the party earlier this year, and said that while "tribal loyalism has its place", the public needed to "vote with your head as well as your heart".

The advice, contained in a video promoting the case for a second Brexit referendum, infuriated the government ahead of a crunch national television debate between Johnson and Labour leader Jeremy Corbyn on Friday night UK time.

"I think it's very sad and I think he's wrong and I think he represents as a view that is outdated, alas," Johnson said.