Boris Johnson has acknowledged it will be a “stretch” to meet his latest leadership campaign pledge to boost police numbers by 20,000 within three years.

Chief inspector of constabulary Sir Thomas Winsor warned on Thursday that the £1.1 billion plan may not be the “most effective” way of increasing police spending.

He warned that recruiting the additional officers would take time and training them would take between 18 months and two years.

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Boris Johnson during a visit to the Thames Valley Police Training Centre in Reading (Dylan Martinez/PA)

Appearing at a Tory leadership hustings in York, Mr Johnson insisted it could be done, although he acknowledged it would not be easy.

“It will be a stretch. You can do about 7,000 or 8,000 a year, it is a stretch. They will come from all over the country,” he said.

“But there’s an imperative to do it. I’ve talked already today to Nick Hurd, the policing minister, and he’s confident we can do it.”

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(PA Graphics)

Earlier Sir Thomas warned that while police forces did need more numbers, that was not the only spending priority.

“You have to invest to be more efficient and that will cost more money. Not all of that money should be spent on hiring people,” he said. “Some of that money should be spent on technology.”

Meanwhile Mr Johnson’s rival Jeremy Hunt suggested he would ease pressure on the social care system by creating incentives for people to look after elderly relatives in the family home.

Jeremy Hunt
Jeremy Hunt in York (Joe Giddens/PA)

Appearing at the hustings, the Foreign Secretary said there were already 420,000 three-generation households with children, parents and grandparents living under the same roof.

“I am not saying we all want to live with our mother-in-law. But I think that three-generation families are a wonderful thing.

“If you look at Spain and Italy, where they spend less on social care than us but they don’t have a social care crisis, it is because they are societies that hold families together.

“As the party of the family, I think we should look to see if we could introduce incentives for that as well.”

Mr Johnson rejected a warning by Chancellor Philip Hammond that the next prime minister would only have the “fiscal headroom” to increase spending if the UK left the EU with a deal.

He claimed that in the event of a no-deal Brexit the Government would be able to draw on the £39 billion saved from the UK’s “divorce” settlement with the EU to spend on other priorities.

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Justice Secretary David Gauke says Parliament will find a way to block no-deal (Dominic Lipinski/PA)

“In the event of a no-deal Brexit, we will have an additional £39 billion to spend,” he said.

Mr Johnson also issued a sharp warning to ministers that he would not brook any dissent over the commitment to take Britain out of the EU by October 31, with or without a deal.

“What I wouldn’t accept is people actively dissenting in public from that policy and undermining it,” he said.

His comments were seen as a thinly veiled swipe at Cabinet ministers like Amber Rudd, David Gauke and Greg Clark who infuriated Brexiteers when they suggested earlier this year they would be prepared to prevent no deal.

They came as Mr Gauke, the Justice Secretary, issued a fresh warning that Parliament would find a way of blocking a no-deal break.

“If I was to speculate on it, given that we have an activist Speaker, given that there is a parliamentary majority against no deal, a way will be found,” he told Parliament’s The House magazine.

Earlier Mr Hunt was forced to deny that he was planning to lift the ban on fox hunting after a newspaper interview in which he said he would vote for repeal if there was another Commons vote,

“The law is not going to change on fox hunting,” he the BBC Radio 4 Today programme.

“There isn’t a majority in the House of Commons and I don’t see there ever being one.”