McDonald’s has admitted 90 per cent of its UK employees are on zero-hours contracts.

The admission indicates the fast-food chain is potentially the largest zero-hours employer in the UK’s private sector, with 82,800 contracted staff not guaranteed work or a stable income.

The controversial practice requires employees to be available for work when it is required but, as they are contracted for 0 hours a week, employers are under no obligation to use them or pay them a set wage.

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This allows businesses not to pay staff during quiet periods, but ensures they are available to work at short notice when required.

Politicians have reacted to McDonald’s admission by calling for it to offer affected staff a new contract with a minimum hours guarantee.

Speaking to The Guardian newspaper, Labour MP Andy Sawford said: “McDonald's could lead on addressing this issue… There will be some employees working 20 to 30 hours a week, week in week out and it is indefensible not to put those people on contracts”.

A spokeswoman for McDonald’s said all those applying for a job with the company are given the opportunity to state which days they can work, with all zero-hours employees told of their shift patterns well in advance.

The spokeswoman said: “We never ask people to be 'on call'... Many of our employees are parents or students who are looking to fit flexible, paid work around childcare, study and other commitments.”

She added: “The zero-hours contracts which all our hourly-paid employees are on do not affect employee benefit entitlement and all of our employees are entitled to a range of benefits including life assurance, employee discounts and access to a range of training and qualifications.”

McDonald’s employs 92,000 staff in the UK, and has admitted to using zero-hours contracts ever since it entered the UK in 1974.

Rival fast-food chains have also been found to be using zero-hours contracts.

Subway admitted using the controversial practice, but said that its stores were independently owned and employment terms and conditions set by the franchisees.

Sandwich chain Pret a Manger, on the other hand, says it guarantees all employees a minimum of eight hours work a week.