Nearly 700,000 people are on zero-hours contracts in their main job - a rise of more than 100,000 on a year ago - according to new official figures.
The rise is likely to trigger renewed debate over the widespread use of contracts that offer no guarantee of hours and only those benefits guaranteed by law, such as holiday pay.
The Office for National Statistics said the number of people estimated to be employed on a zero-hours contract in their main job was 697,000, representing 2.3% of all people in employment. In the same period in 2013, the figure was 1.9% of all people in employment, or 586,000.
Overall, because workers often have more than one job official figures showed the number of employment contracts offering no minimum hours jumped from 1.4m in 2013, to 1.8m last year.
The Labour party and trade unions accused the government of allowing a low-pay culture to grow unchecked, forcing many workers to live a hand-to-mouth existence that often prevented them qualifying for a mortgage.
The ONS said the 28% increase was not so much the result of a surge in the number of zero-hours jobs offered by employers last year, but due more to increasing recognition of the contracts by staff when asked by researchers about their employment terms.
Some of Britain’s largest employers offer zero-hours contracts to employees. High street giants such as JD Wetherspoon, Burger King, Domino’s Pizza, Sports Direct and McDonald’s all use the deals.
The ONS said over half of businesses in the hotel and catering sectors used the contracts and a quarter of businesses in education made some use of no-guaranteed-hours contracts in August 2014.
Universities and colleges have become large-scale users of zero-hours contracts, while an estimated 160,000 care staff are also on similar deals.
Around a third of people on them want more hours, the ONS added, saying people on zero-hours deals are more likely to be women, students in full-time education or working part-time. They are also more likely to be aged under 25, or 65 and over.
Vince Cable said some criticism of employers was valid, especially those that put exclusivity clauses in the contracts, preventing workers from holding more than one job. He is piloting a ban on exclusivity clauses through parliament at the moment.
But the business secretary said the contracts “are valued by many employers and individuals who want flexibility in the hours they work”, naming students, people with caring responsibilities, and those who want to partially retire as beneficiaries.
Labour is expected to say in its general election manifesto that it will change the law so that workers with regular shifts have the legal right to a regular contract.
Chuka Umunna, the shadow business secretary, said Britain’s workers were suffering “a rising tide of insecurity”. He said: “Ministers have watered down every person’s rights at work and zero-hours contracts have gone from being a niche concept to becoming the norm in parts of our economy.
“Labour’s ‘better plan for Britain’s prosperity’ would ban exploitative zero-hours contracts, prohibit employers from requiring workers to be available on the off chance they are needed, ensure zero-hours contract workers who have shifts cancelled at short notice receive compensation and give employees who consistently work regular hours the right to a fixed-hours contract.”
University and College Union general secretary, Sally Hunt, said: “The use of zero-hours and other forms of casualised contracts in education is one of the great scandals of our time. Without a proper contract staff cannot plan their lives on a month-to-month or even a week-to-week basis.”
The ONS added that its consecutive surveys of total contracts were also difficult to compare because they were carried out at different times of the year and prone to seasonal changes in employment practices.
