The Bishop of Norwich last night called on the government to re-think planned welfare reforms which he warned could leave families homeless by forcing them to choose between rent or food.

Bishop Graham James was one of 18 Church of England bishops who signed a letter to a national newspaper criticising the coalition's Welfare Reform Bill which includes a planned �500-a-week benefits cap for families.

The bishops - also including the bishop of St Edmundsbury and Ipswich the Rt Rev Nigel Stock, expressed concern that the policy would leave children facing 'severe poverty and potentially homelessness'.

They supported a series of amendments to the Bill - set to be debated in the House of Lords today - which have been tabled by the Bishop of Leeds and Ripon, John Packer, and drawn up with the help of the Children's Society.

The bishops' criticism of the government was supported by Rowan Williams, the Archbishop of Canterbury, who is a president of the Children's Society.

Bishop Graham told the EDP he felt moved to sign the letter, in which the bishops said the church had a 'moral obligation to speak up for those with no voice', because of wider economic factors.

He said: 'It's because the unemployment figures this week demonstrate just how many people who want a job can't find one.

'The benefit cap, of course, is being introduced to ensure there isn't an incentive to remain on benefits rather than work but it's the way it's being introduced which can penalise children in large families.

'We're asking the government to reconsider the way they're introduced. For example, they could take child benefit out of the equation, which would help children in large families.

'A large family could quickly have to choose between rent and food and become homeless and the cost to society would be much larger.

'The Bishop of Ripon and Leeds is putting down some amendments to the Welfare Reform Bill which I support and I hope the government will think again about the means of introducing this so it doesn't penalise some very poor children in large families.'

The government has said the changes, due to come into effect in 2013, would save �7bn and encourage people on benefits to find employment.

But the Children's Society has warned that a cap on the total benefits households can claim could make more than 80,000 children homeless and push many thousands more into poverty.

It has proposed that the bill should be altered to remove child benefit from household income for the purposes of calculating the level of the cap and has also put forward the option of removing certain vulnerable groups from the cap and providing a grace period for newly unemployed families.

In their letter, the bishops wrote: 'The Church of England has a commitment and moral obligation to speak up for those who have no voice.

'As such, we feel compelled to speak for children who might be faced with severe poverty and potentially homelessness, as a result of the choices or circumstances of their parents. Such an impact is profoundly unjust.'

In addition to Bishop Graham, the letter, sent to The Observer, was signed by the bishops of Leeds and Ripon, Bath and Wells, Blackburn, Bristol, Chichester, Derby, Exeter, Gloucester, Guildford, Leicester, Lichfield, London, Manchester and Oxford.

The policy was defended by the Department for Work and Pensions. A spokesman said: 'It simply isn't fair that households on out-of-work benefits can receive a greater income from the state than the average working household gets in wages. 'This is why we have proposed a benefit cap of around �500 a week.'

dan.grimmer@archant.co.uk