Labour MP Helen Goodman believes that, after the 'bedroom tax' is introduced, some of her unemployed constituents are likely to have only £18 per week left for food.
To show how hard it is to eat reasonably on this, Goodman spent a week on the £18 diet and made a video blog about her experiences.
She found that she ate an average of 400 calories each day less than she needed, leaving her feeling lethargic.
At yesterday's Prime Minister's Questions (PMQs) in the House of Commons, David Cameron disputed the need for benefit claimants to use food banks.
After PMQs, his spokesman clarified the PM's position:
"Benefit levels are set at a level where people can afford to eat. If people have short-term shortages, where they feel they need a bit of extra food, then of course food banks are the right place for that. But benefits are not set at such a low level that people can't eat."
One in five workers is paid less than the minimum amount needed to live on.
Accountants KPMG's report suggests that up to 90% of waiters and bar staff are paid less than this amount.
The living wage is £8.30 per hour in London and £7.20 in the rest of the country.
Unlike the minimum wage, set lower at £6.19 per hour for those aged over 21, the living wage is voluntary, although it has been implemented by a number of companies in London and Manchester City Council.
The number of households where no adult aged 16 to 64 is in work has fallen for the second year in a row, official figures show.
The Office for National Statistics (ONS) said there were 3.7 million such households in the UK between April and June this year, or about 17.9% of all households.
That was down from 18.7% last year, about 3.85 million households.