Greece is "teetering on the brink" - demonstrating the dangers of abandoning the government's economic plan, Prime Minister David Cameron has said.

Speaking at PM's questions, he said it was vital to "learn the lessons of what happens when debt spirals and you lose control of your economy".

The "same old Labour" had not changed its answers on the economy, he added.

Acting Labour leader Harriet Harman said cutting tax credits would be "robbing" from families with children.

There is speculation Chancellor George Osborne will use his July budget to cut tax credits as part of the government's planned £12bn welfare cuts package.

Ms Harman said: "You said in your speech on Monday there is nothing progressive about robbing from our children - but isn't it inevitable that cuts in tax credit for working families, unless employers raise their wages immediately, mean children will be worse off?"

'Robbing from children'

Mr Cameron said he was talking about ensuring the deficit was eliminated and did not rule out cuts to tax credits.

Media playback is unsupported on your device Media caption Harriet Harman tells David Cameron: 'I know he does not have to budget but many families do'

"What we need to do is make sure we go on with the plan that is seeing 2.2 million more people in work and crucially for children, compared with when I became prime minister, there are 390,000 fewer children in households where no one works.

"My programme for tackling poverty is to get more people in work, get them better paid and cut their taxes."

Ms Harman hit back: "I'm asking about robbing from children who are in families who are facing tax credit cuts.

"The IFS have said cutting £5bn from tax credits would mean working families losing on average £1,400 a year."

"I know you don't have to budget but many families do."

Ms Harman urged the jeering Conservative benches to imagine a lone parent working part time.

She said: "To compensate her for a loss of £1,400 a year, the minimum wage would have to go up overnight by 25% - that's not going to happen, is it?"

Mr Cameron said: "The problem is the last government didn't budget for the country."

After an intervention from Speaker John Bercow, he told MPs: "Because the last government didn't budget for the country, as a result the whole country was plunged into poverty which is what we have been dealing with."

A few metres from where the weekly Commons clash was taking place, disability rights protesters were preparing to storm into the Commons chamber and were only prevented from doing so by officials and police who managed to close the heavy wooden doors to the chamber.