Married couples could get a bigger cut in income tax after the election, David Cameron has signalled as he admitted he must do more to win back disgruntled Tories. The Prime Minister said he wanted to 'expand' the marriage tax allowance, which begins next month and is worth £212-a-year for some couples. He said some of his natural supporters had 'drifted' to other parties, as he vowed to stick to his promise to cut net migration to the 'tens of thousands', despite the number soaring to almost 300,000. Scroll down for video . Prime Minister David Cameron has vowed to expand the marriage tax allowance to win back disgruntled Tory supportersa . Under the Tory policy, 4million married couples are in line for the new tax break designed to support for stay-at-home parents. The £1,060 transferable tax allowance will particularly benefit couples where one parent does not work or only works part-time. However, if both people in a couple earn more than £10,600 they will not qualify and higher rate taxpayers earning more than £42,385 a year are also excluded. The idea was first promised by Mr Cameron when he ran for the Tory leadership in 2005, and marks the first recognition of marriage in the tax system since the married couples' allowance was phased out in 1999. It will apply to spouses who do not use all of their personal allowance – either because they are at home looking after children, or work part-time and earn less than the threshold for income tax, £10,600 in April. They will now be able to transfer up to £1,060 of their unused personal tax-free allowance to a spouse or civil partner, as long as the recipient of the transfer pays the basic rate of income tax, levied on income up to £42,385. That will save the couple up to £212 a year on their tax bill. At the Tory spring forum yesterday, Mr Cameron was heckled by party member Mike Howson who said the PM had 'betrayed this country on Europe and immigration' The Conservative Party will spend an extra GBP8 billion on the NHS if it wins the general election to fund a five year plan drawn up by its chief executive, Jeremy Hunt has promised. The Health Secretary said the Government would fully fund the plan drawn up by NHS England boss Simon Stevens, which would see £2billion being pumped into the health service every year until 2019-20. The so-called 'Stevens plan' will see a total of £30 billion put into the NHS, with £22 billion found through efficiency savings and £8 billion in extra spending. Until now only the Liberal Democrats had pledged to find the money but Mr Hunt has signed the Tories up to the plan. Asked by the Sunday Times if the Tories would find the full £30billion, Mr Hunt said: 'Yes. We've demonstrated that we're as good as our word. 'At the last election we were the only party that promised to protect the NHS budget. We didn't just protect it, we increased it. 'We said to Simon Stevens, 'How much do you need for your plan next year, the first year of your five-year plan?' He said '£1.7billion', and we actually found him £2billion. 'We're now doing the work as to what the efficiency savings are. The gap might be more than £8bn, it might be less. 'That will all be settled in the summer when we do the spending-round discussions. We will continue to spend more in real terms year in, year out.' However, the idea was mocked by Lib Dem Deputy Prime Minister Nick Clegg who said the state should not lecture people on their private lives. 'We should not take a particular version of the family institution, such as the 1950s model of suit-wearing, bread-winning dad and aproned, home-making mother - and try and preserve it in aspic,' Mr Clegg said in 2011. 'That's why open society liberals and big society conservatives will take a different view on a tax break for marriage.' However, Mr Cameron has signalled that if he is returned to power he wants to increase the amount that married couples could save on their tax bills. He told the Sunday Telegraph: 'I am very proud to have kept my commitment to introduce the married couples' tax allowance. I think it will prove very popular. 'I think it's absolutely right that we recognise marriage in the tax system properly and I would like to see that expanded.' Mr Cameron suggested that it was part of attempts to win back traditional Tory voters who have switched to other parties, including Labour and Ukip. 'I accept I have a task in the next 41 days to win back people who are instinctively Conservative, who have strong Conservative values and some of them have drifted off to other parties. I need to win them back.' At the Tory spring forum yesterday, Mr Cameron was heckled by party member Mike Howson who said the PM had 'betrayed this country on Europe and immigration'. Mr Cameron has come under fire after promising 'no ifs, no buts' to cut net migration to below 100,000. But latest figures released last week show that a total of 298,000 more people arrived in Britain than left in the year to September, as the numbers arriving from the rest of the EU hit a record high. A record 624,000 arrived in Britain in a year, up from 530,000 in the previous 12 months. At the same time, 327,000 left, a figure which has barely changed since 2010. Net long-term migration to the UK was estimated to be 298,000 in the year ending September 2014, a major rise on the 210,000 figure a year earlier . Some senior Tories urged Mr Cameron to ditch the pledge, but he has vowed to repeat it for the general election this year too. He said: 'Britain is facing quite a lot of pressure because the level of migration has been too high for too long. You see that on school places, and you see that in some places on the health service. 'I can absolutely say to people who are concerned about this, 'I hear you, I hear your concern, I get your message. He insisted he sticks to his pledge: 'you can call it an ambition, you can call it a target. That is what I want to achieve.'
Prime Minister suggests £212-a-year cut could be increased after election . Predicts policy for 4million couples will be 'very popular' from April . Vows to stick to pledge to cut net migration to the 'tens of thousands'
Admits he must do more to win over Tories who 'drifted' to other parties .