ONS admits underestimating number of workers on controversial zero hours contracts

Official figure raised from 200,000 to 250,000 - with promise to change survey on which figures are based

The number of workers employed on zero hours contracts has been underestimated in official figures, the Office for National Statistics admitted today.

The ONS revised its estimate for people working without any guaranteed number of hours up from 200,000 to 250,000. It promised to change the labour force survey, on which the unemployment figures are based, to ensure a more accurate picture of the spread of the controversial contracts.

But unions and think tanks said the ONS is still understating the use of such terms of employment. As The Independent revealed last month, ministers concede that 300,000 people in social care alone work on a standby basis.

Frances O'Grady, the TUC general secretary, said: "These updated figures from the ONS still underestimate the true scale of zero hours working, which has spread like wildfire throughout our economy. 300,000 workers in the care sector alone are employed on these insecure terms and conditions and that is before you factor in sectors like higher education, retail, legal services and journalism."

Ian Brinkley, director at the Work Foundation, said: "We urgently need to bring the various data sources together to get a better idea of the true scale of the use of zero hours contracts and identify where the gaps in our knowledge remain. Without a stronger evidence base about both the numbers of zero hours and how they are used in practice, it will not be possible to develop good policy responses."