Unions have called for action against zero hours working after a study showed about 1.4 million jobs involve contracts that do not guarantee a minimum number of hours.
The Office for National Statistics (ONS) said most of the contracts were zero hours, under which people are not guaranteed work from one week to the next, but officials pointed out that s ome workers could have more than one contract.
A study among employers showed that 13% used non-guaranteed hours contracts, rising to almost half in the tourism, catering and food sectors.
More than one in five employers in health and social work reported using them, but they were relatively rare in financial, manufacturing, energy and agricultural services.
The ONS study of 5,000 employers is the biggest of its type yet and showed the average number of hours on the contracts was 25 a week.
Women, under-25s and those over 65 were more likely to be on zero hours contracts. Two-thirds of those counted worked part-time.
Larger employers were more likely to use zero hours contracts.
TUC general secretary Frances O'Grady said: "Insecure work with no guarantee of regular paid hours is no longer confined to the fringes of the jobs market.
"It is worrying that so many young people are trapped on zero hours contracts, which can hold back their careers and make it harder to pay off debts like student loans.
"The fact that these contracts have become the norm in sectors like tourism, catering and food will be a major concern for the millions of people employed in these industries."
Paul Kenny, general secretary of the GMB, said: "The growing recognition of the extent of exploitation of workers on contracts that do not guarantee a minimum number of hours is welcome and must lead to action to tackle it.
"What is not yet recognised is the extent to which people working on such contracts are blighted in terms of getting credit or entering into rental agreements.
"There has to be an end of exclusivity clauses, minimum hours should be specified in contracts and workers should have the right to claim deemed contractual hours on the basis of their average hours over any 12-week period."
University and College Union general secretary Sally Hunt, said: "Without a guaranteed income, workers on zero hours contracts are unable to make financial or employment plans on a year-to-year, or even month-to-month, basis.
"The use of zero hours and other temporary contracts in education is far more prevalent than many people realise. These contracts deny staff full employee status and key employment rights, while students miss out on a lack of continuity and often receive reduced access to staff employed on minimal hours."
Katie Schmuecker, policy and research manager at the Joseph Rowntree Foundation, said: "Zero hours contracts are just one aspect of the UK's problem with in-work poverty. We have workers unable to get enough hours to lift themselves and their families out of poverty, and not being offered training and development by their employer, leaving them stuck in dead end jobs.
"Tackling in-work poverty requires the nature of jobs at the bottom of the labour market to change, alongside reform to the welfare system."
A Business Department spokesman said: "The ONS's own analysis shows that contracts without a set number of hours - including zero hours contracts - provide important and flexible employment opportunities that suit most people in these jobs and provide an average of 25 hours work a week. Overall they account for around 4% of all jobs.
"It also supports our view that we need to address the issue of exclusivity in zero hours and other variable hours contracts to ensure people are getting a fair deal. Students, older people and second earners want to work flexibly, but we want to make sure they understand what their contract means and that they are not tied exclusively to one employer if it stops them from boosting their income.
"This is what we looked into through our consultation."
John Allan, chairman of the Federation of Small Businesses, said: "Small businesses are by their nature flexible, and the kind of contracts staff are employed on depends on the nature of the business. That said, the ONS figures confirm that small firms are less likely to make use of these contracts than larger businesses and the public sector.
"As a general rule, the FSB believes workers on zero hour contracts should not be prevented from finding other work under so-called 'exclusivity clauses'."
Shadow business secretary Chuka Umunna said: "These shocking figures show that since David Cameron became Prime Minister, there has been a huge increase in the number of people on zero-hours contracts. It is a staggering illustration of the cost-of-living crisis under this Tory led Government and a reminder that David Cameron and George Osborne are failing to deliver a balanced recovery that works for all.
"Labour is clear that we will outlaw zero-hours contracts where they exploit people, ensuring that people at work are protected and get a fair deal. It's time the Tory-led Government matched our plans."
Public and Commercial Services (PCS) general secretary Mark Serwotka said: "Despite the Government and its supporters trumpeting a recovery, these shocking figures are further proof of the weakness of our economy.
"Unemployment remains high and millions of people in work are being forced into insecure jobs for low pay.
"Instead of being complacent about a rise in zero-hour contracts and bogus self-employment, ministers must invest to create real, sustainable jobs and put money back into people's pockets."
Unison union general secretary Dave Prentis said: "The huge rise in these risky employment contracts shows how weak and precarious the labour market is. It is shocking for the Government to brag about a recovering economy when there are more than 1.4 million contracts in use that do not guarantee a minimum number of hours and a regular source of income for workers.
"These figures show that, once again, it is women who are bearing the brunt of this Government's austerity agenda, as they make up the majority of the workforce on unfair zero-hours contracts."
Citizens Advice chief executive Gillian Guy said: "Zero-hours contracts are playing havoc with people's ability to make ends meet.
"As bills rocket and employment remains precarious, people are desperate for stable work. But we see people on zero-hours contracts who are not given any work, leaving them struggling to pay rent, keep the lights on or put food on the table. At the same time, a fluctuating income can make it almost impossible for people to claim in or out-of-work benefits.
"Even if people are getting work, unscrupulous employers are using zero-hours contracts to deny workers their basic rights.
"We help people who have effectively been sacked when employers have cut hours to zero after they become pregnant, take time off sick or ask for changes to their working patterns.
"Others have missed out pay when bosses have exploited loopholes in the law to withhold holiday pay or held up the possibility of more work in the future to stop employees from claiming redundancy.
"This exploitation has no place in the modern labour market."
Business Secretary Vince Cable said: "I welcome the further clarity on zero-hour contracts provided by the ONS. Their own analysis shows that these types of contracts can provide important and flexible employment opportunities that suit most people in these jobs and provide an average of 25 hours' work a week.
"However, it is also clear there has been some abuse of those on zero-hour contracts by some less scrupulous employers. Given the current estimates of people on these types of contracts, it is important we take action.
"That is why I launched a consultation on the issue of exclusivity in zero hours to ensure people are getting a fair deal. Students, older people and people wanting to top up their income want to work flexibly, but we want to make sure they understand their rights and that they are not tied exclusively to one employer.
"We will be publishing the results of this consultation shortly."