Unions are calling for the Government to tackle the rise in zero-hours work after new figures showed a record 905,000 people are employed on the controversial contracts in their main job.
The figure has increased by 101,000 over the past year and now represents 2.8% of all people in employment.
Zero-hours contract workers are more likely to be young, women, part-timers or in full-time education, the Office for National Statistics said.
Those on zero-hours contracts usually work 25 hours a week, with one in three wanting more hours.
Workers employed on the contracts do not know how many hours they will be offered from week to week.
Unite's leader Len McCluskey said: "The Government must act to tackle bogus self-employment and follow the example of its New Zealand counterparts by outlawing zero-hours contracts.
"If we are to build an economy based on decent, secure jobs then insecure working must end."
Unison general secretary Dave Prentis said: "Zero-hours contracts are everywhere in social care.
"They give the upper hand to unscrupulous employers and silence employees who fear they'll lose hours if they speak out about poor practice or illegal pay.
"The lack of regular hours also make it impossible for care workers to know how much they're being paid.
"This lets employers get away with paying below the legal minimum."
Liberal Democrat leader Tim Farron said: "This is a worrying sign that fewer people are finding the long-term, stable jobs they need.
"The Government must give all workers the right to request a fixed-term contract, to prevent people being stuck on zero-hours contracts long-term when they don't want to be."
Jonathan Bartley, Green Party co-leader, said: "The high employment rate masks the insecurity faced by British families.
"Zero-hours contracts are part of a gig economy that facilitates the exploitation of workers and companies are failing to fulfil their moral and legal duty to give their workers secure employment and basic rights."
Tim Roache, GMB general secretary, said: "The number of zero-hours workers is on course to hit one million.
"In the real world, zero hours means zero certainty, zero security, zero ability to plan your life, your future, your family's finances, because from one week to the next, people don't know how much is going to be on their next pay slip."
Dan Tomlinson, of the Resolution Foundation, said: "The number of people on zero-hours contracts has reached an all-time high at the end of last year, further confirming that they are now a permanent feature of our jobs market.
"But the zero-hours juggernaut is showing signs of slowing down, with barely any increase during the second half of 2016."