Beaconsfield MP Dominic Grieve has accused Boris Johnson of 'further radicalising on Brexit' and leaving the UK and leaving the UK with 'starker' prospects by trying to appease hardliners in a strengthening of his stance on the backstop.

The former attorney general also accused him of making a 'disgraceful' suggestion which would "spell the end of democracy as we know it".

On Tuesday, Mr Grieve warned whoever becomes the next prime minister that their government will collapse if they pursue a no-deal departure from the EU.

Mr Grieve said Mr Johnson confirmed that hardliners would 'put up another obstacle' if anyone was able to solve the issue because it is being 'used as an excuse because of this radicalisation.'

Dominic Grieve said: "When challenged and confronted, he radicalised even further and excluded any possibility of trying to negotiate some way out of the backstop at all. It had to go in its totality.

"The consequence of that is (to) make ... the choices starker and starker.

"I've always been willing as a politician to listen to people willing to come up with credible compromises, but what I've found so staggering about the Conservative leadership (contest) is it has been played to a tune of growing extremism."

Speaking alongside Mr Grieve at a second referendum campaign event, Labour MP Margaret Beckett called the candidates' backstop pledges "terrifying" and accused them of throwing "the Irish situation under a bus".

"Nobody can say that that situation is now so peaceful it's inconceivable that there will be further problems in the future. I think that's an extraordinary demonstration of lack of responsibility to the country," she said.