The number of people in the UK with a zero-hours contract as their main job grew by more than 100,000 in the year to November 2015, according to the Office for National Statistics (ONS).
The ONS said there were 801,000 workers on a zero-hours contract as their main job, representing 2.5% of the UK's workforce - up from 2.1% in November 2014.
In total, the ONS estimates that there were 1.7 million zero-hour contracts in the UK in November, suggesting that many people have more than one zero-hour contract. In May, the statistics agency estimated that figure to be in the region of 2.1 million, but stressed that figures can be affected by seasonal factors.
The Trades Union Congress (TUC) described the rise in people on zero-hour contracts as a "nightmare for workers". The union's own research suggest that the average zero-hour contract worker earns £188 per week, compared with full-time employees who earn £479 a week.
The ONS said that most zero-hour contract workers wanted more hours in their current job, rather than a different job that offers more hours. Those most likely to be on a zero-hour contract are young people, women, and those in full-time education.