Voluntary sector organisations are twice as likely to employ people on so-called zero-hours contracts than the private sector, research suggests.
The Chartered Institute of Personnel Development (CIPD) surveyed 1,000 employers for its 2013 Labour Market Outlook.
The institute found that 34 per cent of voluntary sector employers used zero-hours contracts, compared with 24 per cent in the public sector and 17 per cent in the private sector.
It also discovered that 25 per cent of organisations employing 250 people or more used zero-hours contracts compared with 11 per cent of organisations which employ fewer people.
The CIPD defines a zero-hours contract as an arrangement where someone agrees to be available for work as and when required but where no particular number of hours or times of work are specified. Employers are not obliged to offer work to employees on these contracts and workers are not obliged to accept any work offered.
Figures from the Office for National Statistics suggest that approximately 250,000 people in the UK are employed on zero-hours contracts, but the CIPD says its research points to a much higher figure, perhaps as many as one million workers.
The CIPD also interviewed 148 people on zero-hours contracts and its findings suggest a majority were content to work this way, with only 14 per cent of respondents saying their employer did not give them enough work.
The CIPD called for a framework of good practice to be drawn up for zero-hours contracts.
Peter Cheese, chief executive of CIPD, said: "Zero-hours contracts, used appropriately, can provide flexibility for employers and employees and can play a positive role in creating more flexible working opportunities, allowing parents of young children, carers, students and others to fit work around their home lives.
"However, for some this may be a significant disadvantage where they need more certainty in their working hours and earnings, and we need to ensure that proper support for employees and their rights are not being compromised through such arrangements."