The number of workers on zero-hours contracts could be a million - four times higher than official estimates, according to new research.
The Chartered Institute of Personnel and Development (CIPD) said its survey of 1,000 employers showed one in five employed at least one person on a zero-hours contract, under which staff are not guaranteed work one week to the next.
Firms in the voluntary and public sectors as well as hotel, leisure and catering industries were more likely to use the contracts. Separate research among almost 150 zero-hours contract workers revealed 14% said their employer failed to give enough hours for a basic standard of living. Those polled averaged just under 20 hours a week and were most likely to be aged 18 to 24 or over 55.
The Office for National Statistics (ONS) said last week 250,000 people in the UK were on zero-hours contracts at the end of 2012, 50,000 more than a previous estimate after a change in calculating. Unions think this a big underestimation.