One million workers could be on zero-hours contracts - four times as high as official estimates, according to new research.
The Chartered Institute of Personnel and Development (CIPD) said its survey of 1,000 employers showed that one in five employed at least one person on a zero-hours contract, under which staff are not guaranteed work from one week to the next.
Firms in the voluntary and public sectors as well as the hotel, leisure and catering industries were more likely to use zero-hours contracts.
The Office for National Statistics (ONS) said last week that 250,000 people in the UK were on zero-hours contracts at the end of last year, 50,000 more than a previous estimate because of a change in the way the figures are calculated, although unions believe this is a huge under-estimate.
The government is looking into zero hours contracts as new research says the number of people working such contracts could be one million.
Opinion varies dramatically among both workers and employees when it comes to zero hours contracts, as ITV News viewers demonstrate.