After nearly half a century in parliament the 78-year-old is not seeking re-election again

Kenneth Clarke, the Conservative MP whose parliamentary career has just passed its 49th anniversary, says he will most likely not fight another election, even if one is called in the autumn.

Speaking to journalists at a lunch on Thursday, Clarke predicted that neither Boris Johnson nor Jeremy Hunt would end up forcing a no-deal Brexit on 31 October. He said that the “the real world” would take over from the rash promises the pair had made to party members.

Clarke, 78, who has represented the Nottinghamshire borough of Rushcliffe since 1970, now appears to be calling time on his long career. He has held the chancellor, home secretary and education secretary posts among other ministerial roles.

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“You’ve got to hold yourself out for doing five more years and do the job properly,” he said. “I’m currently minded to step down. I’ve told my people in Nottingham that I’m not standing again. I just think in every walk of life, particularly politics, you got to decide to pack it up before people start dropping hints telling you to pack it up because you can’t do it any more.”

Clarke had suggested 2015 would be his last election, but changed his mind and stood again in 2017.

Regarding the promises made by Johnson and Hunt in the Conservative leadership election, Clarke said both Labour and the Tories had been pushed towards more fringe views than those of their MPs after altered rules involving party members electing leaders.

He said: “Both parties were doomed, in hindsight, when they followed the 1990s fashion of making our parties democratic. They’re not ready for it.

“Now we have the membership, which in both parties’ cases is totally unrepresentative of the vote for the respective parties, which now chooses the party leader.

“That’s why it looks like we’re winding up with Jeremy Corbyn and Boris Johnson, who are two of the people most unrepresentative of public opinion at large that you could possibly imagine.”

Johnson has promised to deliver Brexit by 31 October “do or die”, while Hunt has pledged to push for a no-deal departure if needed. Those outcomes were very unlikely to happen whoever won, Clarke said.

He added: “They are pitching themselves at the electorate they are doomed to have to appeal to. I don’t think either candidate believes leaving with no deal makes the slightest sense at all.

“Jeremy hedges it, Boris does his usual thing of changing the way he expresses it day by day. He’ll make his mind up what he’ll actually do, regardless of what he actually said, if he actually finds himself prime minister, and I’m sure Jeremy will start getting back to common sense if he finds himself prime minister.

“Neither of them thinks we’re going to leave with no deal on 31 October. It is, in all practical terms, impossible.”

Facebook Twitter Pinterest Soundbites can be amusing: Ken Clarke chuckles behind Liam Fox and David Cameron at Conservative party conference, 2005. Photograph: Martin Argles/The Guardian

Clarke was dismissive about the leadership campaign as a whole. “When the Conservative party can’t think of anything sensible to do in a crisis it always has a leadership election. And I’ve taken part in several of them.”

He said that in the end “sanity and the real world” would deliver a moderate Conservative government.

“We might return to normality. But it’ll be a different normality. It’ll take a generation to cure the divisions that this issue has caused. It has broken the political system. We will have multi-party parliaments. I think if we had an election, god knows how many parties would be in and what the respective balance would be.”

Clarke reiterated his threat to potentially back a motion of no-confidence against a new Tory government if it pushed for no deal over leaving the EU, saying he faced a dilemma.

“As I don’t think that the declared policy position of either candidate is remotely credible, nor do I think it is what either of them think it is what they’re going to pursue, I shall wait to see what the prime minister says he and the government he forms actually intends to do,” he said.

This, Clarke added, was a luxury he could indulge in as a veteran not seeking to stand again. “I don’t want the new leader to make me parliamentary under-secretary for nuts and bolts.”