Figures released by the ONS this month revealed workers on these contracts – where they have no guarantee of weekly hours or income – have nearly doubled since 2008 to 200,000.
James Lazou, research officer at the UK's largest union Unite, told HR magazine, zero-hours contracts mean employees are obliged to be available for work at the "whim of the employer".
"The assertions that this flexibility, benefits both employers and employees equally are at best deeply naive," Lazou said.
"In low paying sectors, such as the docks, retail, catering and social care, where such precarious work is increasingly becoming the norm, these arrangements serve to trap workers in poverty and exploitation."
He added: "Such insecurity also increases the risk of bullying, harassment and stress."
Former Liberal Democrat treasury spokesman, Lord Oakeshott, said these contracts "cock a snook at the minimum wage", if people have to "hang about" on call unpaid.
He said: "A zero hours Britain is a zero-rights Britain in the workplace -Beecroft by the back door. Being at the boss's beck and call is no way to build a skilled, committed, loyal labour force."
Despite starting off as common practice in the retail and hospitality sector, ONS figures revealed the contracts have now spread to the public services. The number in the NHS has risen by a quarter in two years to nearly 100,000.
Lazou added: "Zero-hour contracts are just the tip of the iceberg. Self-employment has been rising too, with bogus self-employment likely to also be increasing, particularly in sectors like construction, agriculture and hospitality.
"The reality is that Britain has one of the most deregulated labour markets in the EU, yet our economy is still stagnating badly. Tackling underemployment, low pay and exploitation must be part of the solution, otherwise where will it end?"
According to the Government, people on zero-hours contracts are classed as "being in employment regardless of the number of hours they actually work" – even if they remain on standby all week without being paid.
