The shadow home secretary stumbled over the cost of plans to put 10,000 extra police on the street in awkward exchanges with LBC’s Nick Ferrari.
In one attempt to come up with the bill for the flagship policy, officers would earn just £30 while a second go left them with £8,000.
Ms Abbott’s assessment of how many new officers would be recruited in the first 12 months of the four-year plan ranged from 25,000 to 250,000,
The shadow cabinet minister told BBC Two’s Daily Politics: “I do know my figures. I did seven interviews that morning and that was the seventh and I mis-spoke but I do know my figures.”
Jeremy Corbyn said the policy would cost £300 million, and insisted he is “not embarrassed in the slightest” by Ms Abbott’s gaffe.
“She corrected the figure and that’s the figure and it will be paid for by not going ahead with the cuts in capital gains tax,” he told Sky News. Asked if it was embarrassing that Ms Abbott got the figures wrong, he said: “Not at all. We have corrected the figure and it will be absolutely clear now, today and in the manifesto.
“I’m not embarrassed in the slightest.”
The gaffe was quickly seized on by the Conservatives, who claimed it showed that Labour’s sums “don’t add up”.
Home Secretary Amber Rudd said: “Diane Abbott has laid bare the chaos that Britain would face if Jeremy Corbyn is voted into Downing Street.
“One of Corbyn’s closest allies has clearly shown that Labour’s sums don’t add up, they would weaken our defences, and their nonsensical promises aren’t worth the paper they are printed on.”
Ms Abbott repeatedly paused and stumbled as she gave a range of figures for how many extra officers would be recruited and what the bill for the plan would come to.
She initially said the four-year project would cost £300,000, then revised it up to £80 million before finally landing on £718 million.
Although the plan is to recruit 10,000 officers, Ms Abbott said 25,000 new recruits would be brought in annually, before later saying 250,000 policemen would be employed in the first year of the scheme.
She told LBC: “Well, if we recruit the 10,000 police men and women over a four-year period, we believe it will be about £300,000.”
Ferrari replied: “£300,000 for 10,000 police officers? How much are you paying them?”
Ms Abbott replied: “No, I mean, sorry, they will cost, it will cost about, about £80 million.”
“About £80 million? How do you get to that figure?” he said.
Ms Abbott answered: “We get to that figure because we anticipate recruiting 25,000 extra police officers a year at least over a period of four years.
“And we are looking at both what average police wages are generally, but also specifically police wages in London.”
Ms Abbott went on to say that, in the first year of the scheme, the party expected to recruit 250,000 policemen.
“The figures are that the additional cost in year one, when we anticipate recruiting about 250,000 policemen, will be £64.3 million,” she said.
When Ferrari queried the figure of 250,000 policemen, Ms Abbott responded: “And women.”
Challenged again on the figure, she said: “No, we are recruiting two thousand and - perhaps - two hundred and fifty.”
Ferrari asked: “So where did 250,000 come from?”
Ms Abbott responded: “I think you said that, not me.”
He replied: “I can assure you you said that, because I wrote it down.”
Ms Abbott then said: “What I am saying about the cost is that in year one, obviously, we are getting ready to recruit.
“But in year two, the cost will be £64.3 million. In year three, the cost will be £139.1 million. Year four the cost will be £217 million. And year five, the cost will be £298 million.
“And that can be amply covered by reversing the cuts in capital gains tax.”
Starting salaries for police officers in England and Wales range from £20,000 to £23,000.