Bullying-accused David Cameron says he has duty to warn of Brexit dangers

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With just 10 days until the country decides on Britain's future in the bloc, he conceded that it remained a "very lively and very full debate" amid claims of panic in the Remain camp.

But he said the pro-EU side "have the most confident and the most positive case that we can carry on making this country greater if we stay in".

Ukip leader Nigel Farage downplayed the economic implications of victory for Vote Leave, suggesting some short-term turbulence could be beneficial and dismissing claims the pound was already under pressure.

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"Since Brexit became a possibility, sterling is up and FTSE is exactly the same level it was in March. These are ludicrous scare stories that are being put out," he told BBC1's Andrew Marr Show.

"Even if Sterling were to fall a few percentage points after a Brexit, so what? The point is we have a floating currency and it would be good for exports."

Mr Cameron hit back: "I'll tell you 'so what'. If the pound falls then that means the prices in our shops go up, the weekly shop costs people more, that family holiday costs more. These are all risks we should avoid and we shouldn't risk it."

He told the show: "I totally accept that people are confused by having so many statistics and that there is a lot of frustration because of that.

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"But I think it is actually my job as Prime Minister, when you have got information coming from independent forecasters ... to talk about those risks and it would be very irresponsible not to."

Backing Brexit was voting for the first self-inflicted recession, he said.

The Remain camp sought to press home its central message of likely economic turmoil in the event of a vote to quit the bloc on June 23 amid signs of a hardening of public opinion against the EU.

The PM told the Observer: "If we leave the EU, independent and respected experts like the IFS and the NIESR say that by 2020 we will face a black hole in our public finances of up to £40 billion.

"In those circumstances, future funding for the NHS could be at risk. Our ability to ring-fence and protect spending on health could be at risk too.

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Writing in the Sunday Telegraph, the Prime Minister said ministers would be "forced" to re-examine pensioner benefits.

"We've made a special effort to protect pensioners," he said - highlighting the "triple lock" which says the state pension will rise in line with earnings, inflation or by 2.5%, whichever is higher, and the protection of bus passes and free TV licences.

"We did all this in the expectation of a growing economy. But if we had a big black hole, we could struggle to justify this special protection any longer.

"In fact, even if we could justify it morally, it wouldn't actually be affordable. Not when pensions represent a huge portion of public spending - over £90 billion this year - and when inflation is forecast to hit 4% if we leave Europe.

"So here is the reality: if we leave, the pensioner benefits would be under threat, and the Triple Lock could no longer be guaranteed in the long term."

Pro-Brexit ex-Cabinet minister Iain Duncan Smith accused his party leader of a "vindictive and desperate attempt to bully and frighten the British people".

"This is a baseless threat," he said.

"What we now have is a vindictive and desperate attempt to bully and frighten the British people - particularly pensioners - all in a frantic bid to rescue a failing campaign."

Labour said a post-Brexit squeeze on the public finances could result in charges for GP appointments and NHS hospital stays.

Amid concerns the party's core support is being drawn increasingly towards a Leave vote, the Opposition is stepping up warnings of the prospect of the country being run by a right-wing Eurosceptic Conservative government.

Shadow health secretary Heidi Alexander said: "If we leave Europe, most experts agree that the economy will suffer and this would mean an even deeper black hole in NHS finances.

"This translates into staff cuts, service closures or charges being introduced.

"A post-referendum Government led by Boris Johnson could mean people turning up at A&E or to see their GP and having to reach for their credit cards. I don't think that's right and I don't think many patients do either.

"The leave camp needs to come clean with the British public and admit a vote to leave Europe puts the NHS at risk."

Clare Gerada, a GP and former chairwoman of the Royal College of General Practitioners, added: "Boris and his friends don't believe in our National Health Service and would jump at the chance to make people have to pay to use it.

"That would be bad for patients and bad for the nation's health. It would also mean more administrative work for already overstretched staff."

Meanwhile, Labour's shadow chancellor John McDonnell blasted both sides of the EU referendum campaign as he spoke to the Peston On Sunday programme on ITV.

He said: "I think I'm where most people are at at the moment in terms of I'm fed up of 'Project Fear' on both sides.

"I think what's been happening is there have been exaggerated claims on both sides and that's turned people off."

Mr McDonnell was asked if Mr Cameron was wrong to claim that public services could be cut if the UK backs Brexit.

He said: "It is true that there are risks to our economy because our economy is fragile and I blame the Tories for it being so fragile."

He added: "I do not want anything putting people's pensions at risk and there could be that risk - this is a big leap in the dark."