Almost 700,000 people in the UK are on zero-hours contracts, equating to more than 2% of the workforce, according to official figures from the Office for National Statistics (ONS) reports The Independent.

The data shows that 697,000 people were employed on a zero-hours contract in their main job between October and December 2014. The figure marks an increase of 18.9% from the 586,000 recorded in the same period in 2013 and represents 2.3% of all people in employment.  

However, the ONS noted that it was unclear whether the rise was due to more people being employed on a zero-hours basis or to more workers recognising the term as applying to them.

On average a person on a zero-hours contract works 25 hours per week, with a third desiring more hours. Women, those in full-time education, and part-time workers are most likely to be on a zero-hours contract, as are those aged under 25 or over 65.

Additional data shows that businesses used 1.8 million zero-hours contracts in the two weeks beginning 11 August 2014. This compared to 1.4 million for the fortnight beginning 20 January 2014, but the seasonal variations meant a direct comparison was not possible.

The industries most likely to offer zero-hours contracts are accommodation and food, followed by education.

In June, the Government announced that it would ban exclusivity clauses in zero-hours contracts that prevent employees from working for additional employers.

But unions have urged the Government to go further.

Frances O’Grady, General Secretary of the Trade Union Congress (TUC), said: "Zero-hours contracts sum up what has gone wrong in the modern workplace. They shift almost all power from the worker and give it to their boss. Anyone on such a contract has no guarantee of any work from one day to another. Put a foot wrong, and you can find yourself with little or no work.”

"Employers often argue that they offer flexibility, but trying telling that to zero-hours workers who can’t get a mortgage or pay their rent. In many sectors, especially social care, zero-hours contracts are used to drive down costs regardless of the impact on services and the workforce."

However, the Institute of Directors (IoD) said that zero-hours contracts protect the UK from European levels of unemployment.

Christian May, Head of Communications and Campaigns at the IoD, said: "Given the consensus that now exists on ending the exploitative use of exclusivity clauses, what remains of the debate is largely semantic. Those who wish to hold up zero-hours contracts as a symptom of an unfair economy will continue to do so, but they must appreciate that for hundreds of thousands of workers and employers these contracts represent an extremely attractive proposition.”

“Despite efforts to portray all those on such contacts as exploited, the truth is that there are plenty of engineers, contractors and professionals whose willingness to be flexible adds significantly to their market value and, therefore, their earning power.”

"It’s also worth remembering that a flexible labour market, of which cero-hours contracts are a vital component, has protected the UK from European levels of unemployment. Indeed, the UK’s labour market has been singled out for praise by the OECD. The alternative is a rigid labour market and high unemployment," she added.