Around 92,000 members who no longer even represent Conservative voters have crowned the “clown prince” as our prime minister. Just when we need a prime minister to bring us together, lead us through the Brexit crisis and on to tackling the serious issues we must confront, the party serves up Boris Johnson. His lifelong ambition has finally been realised; no one and nothing was going to get in his way this time, least of all integrity and truth.

What Boris Johnson hasn’t done is tell us how he is going to ensure we leave the EU on 31 October

The leadership hustings, far from allaying profound fears about Johnson’s ability and mendacity, went further than merely confirming them. Under friendly fire, he revealed he is actually worse than we had thought.

The hustings also revealed the real Conservative party and its drift to the right. It wasn’t simply that the members don’t look like today’s UK – 71% male and 97% white – it was more about what they said. And the regular applause for Johnson’s dog-whistle rightwing rhetoric proved – as did the election result – that Tory members were prepared, indeed pleased, to lose jobs and the union rather than lose their precious no-deal Brexit. That move to the right, away from the centre ground inhabited by One Nation Conservatives, was the major reason I left the Tory party, after serving it as an MP for nine years.

Johnson is the man who wrote in June 2016, following the referendum, that “the only change – and it will not come in any great rush – is that the UK will extricate itself from the EU’s extraordinary and opaque system of legislation”. He soon changed his mind, agreeing as a member of the cabinet to considerably more “changes”, notably our departure from both the single market and customs union. In late 2017 Johnson approved the foundations of Theresa May’s withdrawal agreement but, true to form, changed his mind and resigned when it became a reality. In March this year, Johnson voted for the withdrawal agreement he had described as an “absolute stinker” and the Irish backstop he’d labelled a “constitutional abomination”. Really there’s no end to his shame. Now he threatens a crash-out “do or die” with a no-deal Brexit by the end of October, though he claims there’s only a million to one chance of it happening. Little wonder he is known as the “great charlatan”.

Even before Johnson had been announced as the winner, ministers who had worked with him were queuing up to resign – he has already proven to be the most divisive prime minister ever, and that’s just in his own party. Johnson has a record of ineptitude and irresponsibility, leading to an almost universal verdict that he was the worst foreign secretary in living memory. Johnson has a reputation for laziness and not reading his briefs, and however good his civil servants and the recall of the small army of competent people who protected him as mayor of London, these fundamental flaws will be exposed as prime minister – bluster and buffoonery will not do.

Now he is determined to deliver no deal – a grossly irresponsible Brexit. The 2016 leave campaign leaders, like Johnson himself, specifically promised this wouldn’t happen. His vision has been embraced by the Conservative party, yet further evidence of its race to the right. Johnson now represents an ideologically driven party determined to crash us out of the EU in defiance of the needs and wishes of millions of hardworking people.

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What Boris Johnson hasn’t done is tell us how he is going to ensure we leave the EU on 31 October. The EU is adamant the negotiations are closed. In any event, the commission will not be in place until November – one of those details that Boris ignores. It is genuinely difficult to see any Boris-wrestling or any sweetener that could make May’s deal more palatable to the DUP and the European Research Group rebels. Last week’s vote by parliament, in effect, again showed a majority against any crash-out, no-deal Brexit. So how is Johnson going to achieve his promise? Admittedly, as the evidence shows, his standout ability is to change his mind to suit his purpose and audience.

Johnson’s vision has been embraced by the Conservatives. The dominant force of ideologically driven rightwing hard Brexiteers will be the party’s downfall. They would sacrifice the economic future, notably for our young people.

The Tories always used to put the country’s economic interests first. British voters should not forgive them for abandoning the pragmatic centrist policies that once made the Conservatives the natural party of government.

• Anna Soubry is a former Conservative MP and now leader of The Independent Group for Change