Mr Johnson responded by saying: “I think it’s very sad and I think that he’s wrong.”
Sir John, backing ex-ministers David Gauke, Dominic Grieve and Anne Milton, said in a pre-recorded video message played at a pro-second referendum rally in London: “Let me make one thing absolutely clear: none of them has left the Conservative Party, the Conservative Party has left them.
"Without such talent on its benches, Parliament will be the poorer, which is why – if I were resident in any one of their constituencies – they would have my vote.”
Sir John described Brexit as the “worst foreign policy decision in my lifetime”, and will say leaving the EU will affect “nearly every single aspect of our lives for many decades to come”.
He will say: “It will make our country poorer and weaker. It will hurt most those who have least. Never have the stakes been higher, especially for the young. Brexit may even break up our historic United Kingdom.”
Tony Blair, the man who replaced him in office in 1997, also appeared at the rally.
Mr Blair warned voters not to give the Tories a majority on December 12.
“It’s not Brexit that’s getting done. We’re getting done. This is the final chance for a final say. It’s not one General Election but 650 individual ones. Think long. Think hard. Time to choose. Choose wisely.”
Sir John’s and Mr Blair’s attempted interventions came as Mr Johnson unveiled a new election poster in a visit to Kent.
It declares: “Get Britain out of neutral.”
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