Nearly 700,000 people were employed on a controversial zero hours contract for their main job in December 2014, making up 2.3% of all people in work, official data has revealed.
The Labour Force Survey figures, released by the Office for National Statistics, show an increase of more than 110,000 cases from the same period in 2013.
Accounting for those with more than one job, the total number of contracts in use that do not guarantee work reached 1.8 million in August 2014, according to a separate survey of employers by the ONS. This is up from a 1.4 million estimate published in January 2014. However, a direct comparison of the data is difficult due to seasonal industries.
It comes as Sports Direct boss Mike Ashley is being summoned before the Commons to discuss claims of staff mistreatment. Nearly 300 of its part-time employees are pursuing a legal claim against the retailer over claims they were excluded from its bonus scheme as a result of being on the contracts.
Additional information shows that on average a worker on a zero hours contract usually works 25 hours a week, with around a third wanting more, compared with 10% of those in fixed-hour employment.
Women, those in full-time education and those between the ages of 25 or 65 are most likely to be employed under the terms.
The size of the business also affects the likelihood of a zero hours contract being used. Businesses that employ 250 or more staff are five times as likely to use them than one that employs fewer than 20.
The ONS said the results of the Labour Force Survey could be affected by a greater number of respondents understanding the term compared to previous years.
Neil Carberry, director for employment and skills at the Confederation of British Industry, said: “While there has been an increase in the use of these contracts, they are still only used by just over 2% of the entire labour market.
“The important thing is to ensure that action taken to avoid any abuses doesn’t restrict the use of flexible contracts - figures show that almost two thirds of people are satisfied with the number of hours they work, and being in work gives people more opportunities to increase their hours,” he added.
Last week Labour leader Ed Miliband said in a speech that a Labour government would ban the use of the contracts while the Conservative Party has said it would focus on stopping abuse of the terms.