The prime minister and deputy leader of the opposition, Harriet Harman, have clashed over cuts to the police budget in Greater Manchester.
Hundreds of police staff have spent the day finding out if their post in the force will be lost.
Greater Manchester Police (GMP) needs to shed almost 3,000 posts to save £134m over the next four years.
David Cameron told the Commons the force needed to shift its resources to the frontline.
The exchange during prime minister's questions came after Ms Harman raised a report by GMP chief constable Peter Fahy which revealed that frontline police officer posts would be cut.
Back office staff
She said: "What does he say to the people of Greater Manchester who will be deeply worried about the cut in police numbers?"
Mr Cameron replied: "The chief constable of Greater Manchester has said that his plans are putting the maximum resources on frontline policing."
The prime minister went on to outline figures for the number of people employed in GMP back office departments such as human resources and finance.
"Guess how many people are involved in IT in Greater Manchester Police? Two hundred and twenty five," said Mr Cameron.
"Now this is the debate we ought to be having, how do we get resources from the back office on to the frontline?
"How do we do it, when right now only 11% of police officers are on the streets at any one time. That's the mess we've inherited, that's the mess we're going to clear up."
The chief constable announced on Monday that 750 civilian employees and 309 officers would go by 2012, with more to follow. A total of 1,387 officers and 1,557 civilian posts could go in the next four years.
Staff members had one-to-one meetings with their managers on Wednesday to find out what the future holds for them.
One IT worker, Margaret Haydock, was told her job was disappearing as a result of the savings measures.
In response to Mr Cameron's comments, she said: "What's going to happen when we're not there? Who is going to support the officers when they can't work something out?"
"When their computers break who's going to come and fix them? That's back office staff."