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.
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.”
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.
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.”