Supermarkets have dismissed claims they are using benefit claimants as "forced labour".

Members of the Boycott Workfare campaign protested outside the Welfare to Work conference last week dressed as a chain gang and brandishing signs accusing supermarkets of paying claimants on work placements only 3p a minute to stack shelves.

Sainsbury's said it had employed thousands of people following the work placements.

Tesco said it was providing 3,000 four-week-long work placements this year.