text: George Osborne was challenged 18 times yesterday to explain where the next Tory government would find the extra £8billion it has promised the NHS. During tense exchanges with the BBC’s Andrew Marr, the Chancellor repeatedly ducked questions about exactly how the massive cash boost would be paid for. Mr Osborne said it would come from the Conservatives’ ‘balanced plan’ for the economy, but declined to go into further detail. Scroll down for video . Chancellor George Osborne and Labour Deputy Leader Harriet Harman, appearing on BBC1's The Andrew Marr Show . In one exchange, Mr Marr said: ‘You’ve just found an extra £8billion. All I’m asking is where does it come from? No higher taxes, extra public spending cuts? Where?’ Mr Osborne replied: 'Well it’s part of our balanced plan. And if you look over the last five years …’ But Mr Marr interjected: ‘That’s not really an answer, Chancellor.’ Harriet Harman was left squirming yesterday after ‘posh’ George Osborne revealed on the Andrew Marr show that they had attended the same £21,000-a-year private school. She went to St Paul’s Girls’ school in West London while Mr Osborne attended the boys’ school. During tense exchanges with the BBC’s Andrew Marr, the Chancellor repeatedly ducked questions about exactly how the massive cash boost would be paid for . Mr Osborne insisted, however, that the Conservatives had shown in government that they were able to make the savings necessary to deliver additional funding for the NHS. Migrants will have to pay in more than £20,000 in taxes before they receive access to the benefits system under Tory plans. Home Secretary Theresa May said the new rules would end welfare tourism and make the UK less attractive to Eastern European migrants. New arrivals will be banned from claiming benefits until they have paid into the system for four years. The plan to ensure that they have to pay £22,600 in tax and national insurance before they can claim a penny will be part of the Tory manifesto. European job hunters would be denied unemployment benefits and forced to leave within six months if they do not find work. Those who get a job would be denied in-work benefits, including council housing, for four years. They will also be refused child benefit for offspring living anywhere else in Europe. ‘We have a balanced plan to grow our economy, to make savings in government including in welfare to fund our NHS each and every year,’ he said. ‘We have to make similar savings each year that we have made for five years of this parliament but for two years. ‘We have a track record in this parliament where we found almost £8billion extra in real terms for the National Health Service in very, very difficult economic circumstances so we have proved our mettle, we have proved our ability to stand behind the National Health Service in this parliament. We can do it in the next.’ Labour deputy leader Harriet Harman, who also appeared on the programme, said the promise was ‘illusory’ and that Tory spending plans represented a ‘real threat’ to the health service. ‘The reality is that the spending programme that they have put forward is a threat to cut the NHS,’ she said. ‘People know that they find it harder to see their GP since the Tories came into government, they know that they wait longer in accident and emergency and that waiting lists are starting to grow.’
target: During exchanges with  Marr, Chancellor repeatedly ducked questions .
  Mr Osborne only said it would come from Conservatives’ ‘balanced plan’
  Labour deputy leader Harriet Harman said the promise was ‘illusory'