Oxfam has accused British supermarkets of inflicting poor working conditions on millions of women workers in their efforts to conduct price wars.

A study of employment conditions in 12 countries by Oxfam found that the largely female workforce in many suppliers is working loner hours for low wages in unhealthy conditions.

Kate Raworth, the report’s author, said: “The majority of worker’s performing these tasks such as picking fruit and cutting flowers are women. But rather than their work providing the income to lift their families out of poverty, these worker are commonly hired on short contracts or, with no contract at all, they have no sick leave and their insecurity and vulnerability is reinforced.

The report also says that retailers are now holding internet auctions for suppliers to submit the lowest bids for contracts and place same-day orders for fresh produce to be packaged and shipped within 24 hours, placing extra burdens on female pickers and packing workers.