A leader within the Conservative party has challenged a Church-backed advertising campaign that labels benefit cuts as the reason for an increase in food poverty in the UK.

The ad, which echoes the famous 1979 Conservative election poster 'Labour Isn't Working', shows a line of people queuing up to visit a food bank under the slogan 'Britain Isn't Eating'.

Church Action on Poverty is behind the campaign and is calling for the government to address the exponential increase in food poverty in Britain. It is urging David Cameron to make fundamental changes to benefit cuts in order to give vital support to families in need.

"Thousands are going hungry because of benefit changes," the ad reads.

"Call for urgent action."

The ad has provoked an angry response from Tory MP Iain Duncan Smith, who accused charities campaigning against benefit cuts of "scaremongering".

Church Action on Poverty claims that over 500,000 people, a third of whom are children, have had to resort to using food banks this year, and says that "the single most common reason for people to need food aid is that their benefits have been changed, delayed or stopped".

Tory MP for Banbury and Churches Commissioner Sir Tony Baldy revealed the results of a recent survey that found 62 per cent of those who use food banks do so because of low income, 42 per cent as a result of benefit changes, and 35 per cent due to delays in receiving benefits.

In response to this, however, a spokeswoman for the Department for Work and Pensions has claimed there is "no robust evidence" that welfare reforms are linked to the increase in use of food banks. She asserts that the benefits system does in fact support millions who are on a low income or unemployed.

The DWP claims that more people are using food banks simply because the Trussell Trust, which runs 400 food banks across the UK, is opening three new ones every week, and that "awareness has helped to explain their recent growth".

Mr Duncan Smith wrote a letter to the chairman of the trust, Chris Mould, saying: "I strongly ask you to refute this claim and would politely ask you to stop scaremongering in this way.

"I understand that a feature of your business model must require you to continuously achieve publicity, but I'm concerned that you are now seeking to do this by making your political opposition to welfare reform overtly clear."

The Trussell Trust, however, has rejected the claims of political motivation and Church Action on Poverty has labelled the increase in food poverty "a national disgrace".

"It undermines the UK's commitment to ensuring all its citizens have access to food – one of the most basic human rights," its website says.

The Trussell Trust has repeatedly asked for meetings with government officials to address the issue of food poverty in the UK, but these have so far been denied.

Mr Mould told the Independent: "We are deeply disappointed, but we are as open as ever to meet ministers in the hope that perhaps the New Year will bring a fresh approach to what could so easily have been a fruitful dialogue."