Deputy Prime Minister Nick Clegg has defended the coalition's welfare reforms in the face of the latest onslaught from the church, insisting it is right to withdraw benefits from claimants who refuse to look for work.

The Liberal Democrat leader rejected claims made by Anglican bishops and other faith leaders that the Government was taking a "punitive" approach to welfare claimants.

And he accused the Archbishop of Westminster, the Most Rev Vincent Nichols, of exaggerating the extent to which people had been hit by the changes.

His intervention came after 27 Anglican bishops signed a letter to the Daily Mirror warning that thousands of people were being forced to rely on handouts from food banks as a result of the Government's benefit changes.

Their comments echoed recent remarks by Archbishop Nichols - the leader of the Roman Catholic Church in England and Wales who is shortly to be made a cardinal - who said it was a "disgrace" that in such a wealthy country there were people who could not afford to feed themselves.

Meanwhile, a cross-party group of MPs and peers has announced that it is staging a far-reaching inquiry into the whole issue of "hunger and food poverty" in Britain.

Speaking on his weekly radio phone-in on LBC, Mr Clegg insisted that at a time of major cut backs to public spending, the welfare budget could not escape unscathed. But he said the Government's reforms were designed to encourage people back to work.

"I have a huge amount of respect for Vincent Nichols, but I think that to say that the safety net has been removed altogether is an exaggeration, it is not right.

"I think most people in this country accept that of course you need to have a safety net, of course you need to give help to people that are vulnerable, but for those who have been given support to go out to look for work, there has to be some kind of conditionality.

"You can't just be given benefits with no strings attached and with no questions asked, when you (are) being given support to find your way back into work."

In their letter, sent to mark the beginning of Lent on March 5, the bishops said that 500,000 people had visited food banks in the UK since last Easter while 5,500 had been admitted to hospital in the UK for malnutrition last year.

They said that politicians had a "moral imperative" to do more to control food price hikes and to make sure that the welfare system offered the poor an essential safety net from hunger.

"We must, as a society, face up to the fact that over half of people using food banks have been put in that situation by cut backs to and failures in the benefit system, whether it be payment delays or punitive sanctions," they wrote.

"We call on government to do its part: acting to investigate food markets that are failing, to make sure that work pays, and to ensure that the welfare system provides a robust last line of defence against hunger."

Conservative MP Laura Sandys, who is taking part in the cross-party inquiry organised by Labour's Frank Field, said they would be looking at the food system in its totality.

"You look at the people who are going to food banks, it's not just people who are on benefits, it's also people on low incomes and I think we have to be really clear there might be something systemically wrong with the food system," she told BBC Radio 4's The World At One.

"There is obviously very tight need and very tight concerns by families who are low income, who are facing all sorts of different decisions in their lives."

Signatories to the letter included Anglican bishops Stephen Patten (Wakefield), David Walker (Manchester), Tim Stevens (Leicester), Andy John (Bangor), Tony Porter (Sherwood), Paul Butler (Durham), Alan Wilson (Buckingham), Alan Smith (St Albans), Nick Holtam (Salisbury), Tim Thornton (Truro), John Pritchard (Oxford), Steven Croft (Sheffield), Jonathan Gledhill (Lichfield), Michael Perham (Gloucester), Alastair Redfern (Derby), Lee Rayfield (Swindon), James Langstaff (Rochester), Martin Warner (Chichester), Mike Hill (Bristol), Martin Wharton (Newcastle), Peter Maurice (Taunton), Gregory Cameron (St Asaph), Peter Burrows (Doncaster), Stephen Cottrell (Chelmsford), Martyn Snow (Tewkesbury), David Urquhart (Birmingham) and John Holbrook (Brixworth). They were joined by a number of Methodist Districts and the Quaker Peace and Social Justice group.