Councils have been urged do more to combat zero-hours contracts, after figures suggested their use has jumped by almost 20% in the last year.
Data from the Office for National Statistics (ONS) reveals the number of workers who claim to be on a contract with no guaranteed hours rose to 697,000 - or 2.3% of all people in employment.
This marks an increase of more than 100,000 people working under zero hours contracts on estimates for the period of October to December 2013.
Trade union leaders today urged local authorities to root out use of these 'Victorian style contracts' by firms bidding for town hall work.
ONS research into employers suggests that of the 5,000 companies sampled in the fortnight beginning August 2014, 1.8m contracts provided no guaranteed hours - up 1.4m on previous samples. Figures suggest that larger companies were also more likely to use zero hours contracts, with half of businesses with 250 employees or more making use of such contracts compared to only 10% of firms with less than 20 employees.
Unison general secretary, Dave Prentis (pictured), said: 'Any local authority or NHS trust paying for services from local employers should be making sure that none of the successful bidders are exploiting zero-hours workers.
'Rather than see a decline in the use of these casual contracts as the economy improved, today's figures show zero-hours are booming. In fact this way of working has now become standard practice in the social care sector. This is bad news for social care workers and the people they care for. There's no doubt that zero-hours suit a small number of workers but for most this way of working is far from ideal.'
TUC general secretary Frances O'Grady added: 'Zero-hours contracts sum up what has gone wrong in the modern workplace. They shift almost all power from the worker and give it to their boss. Anyone on such a contract has no guarantee of any work from one day to another. Put a foot wrong, and you can find yourself with little or no work.
'In many sectors, especially social care, zero-hours contracts are used to drive down costs regardless of the impact on services and the workforce.'
