The officer questioned the Prime Minster on how many extra police the Goverment was planning to introduce after the "horrible Manchester attack".
Responding to the probe, Mrs May said the Tories were adding more money, adding her party was planning for the future.
The Tory leader also said "policing will be different" and her party would be investing in cyber security.
But in the TV host quizzed the Prime Minster on current police numbers, adding: "Isn't that a drop of 20,000?"
Theresa May was quizzed about how many extra police officers there will be after Manchester
Mrs May replied: "What we had to do when we came into government in 2010 was to ensure that we were living within our means and that was very important because of the economic situation we had inherited.
"It's not just about the numbers of police – people often focus on the numbers of police. It's actually about what the police are able to do and how they are being deployed on our streets.
"In counter-terrorism policing we have protected those budgets and we are currently protecting police budgets.
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Jeremy Corbyn during a visit to Hackney Marshes Football Pitches, to highlight Labour's manifesto commitment to ensure 5% of the Premier League's television rights income is diverted to the grassroots game, during a General Election campaign
Mrs May said crime is changing and the Government would be focusing on the emerging cyber-crime
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Isn't that a drop of 20,000?
She added: "But crime is changing and the sort of job that the police officers need to do is changing. That's why we are also putting extra money into things like cyber-crime, because that's today's world.
"A government has to ensure that we are keeping abreast with the changes that take place, with the challenges out there that we need to deal with.
"Of course the terrorist threat is severe, but that's why we ensure that our police, our security service have that counter-terrorism budget and we are increasing the budgets for our security services, but also that they have the powers they need to do the job."