ONE million UK workers may be on controversial zero-hours contracts, according to new research.

The figure, four times the official estimate, has been produced by the Chartered Institute of Personnel and Development (CIPD) after it surveyed 1000 employers.

It found one in five had at least one worker on a zero-hours contract, under which staff are not guaranteed a set amount of work.

Firms in the voluntary and public sectors, as well as the hotel, leisure and catering industries were more likely to use such contracts.

Separately, almost 150 zero-hours contract workers said their employer failed to give them enough work to have a basic standard of living.

The workers polled ­averaged just under 20 hours a week and were most likely to be aged between 18 and 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 last year, 50,000 more than a previous estimate.

CIPD chief executive Peter Cheese said: "Zero-hours contracts are a hot topic and our research suggests they are being used more commonly than the ONS figures would imply. However, the assumption that all zero-hours contracts are bad and the suggestion from some quarters that they should be banned should be questioned.

"There does need to be a closer look at what is meant by a zero-hours contract, the different forms that they take, and clearer guidance."

Business Secretary Vince Cable has ordered a review of zero-hours contracts, saying little is known about their impact on firms and staff.