McDonald's workers stage first ever strike in pay and conditions row
The Bakers, Food and Allied Workers Union (BFAWU) said the strike was being well supported.
Members of other trade unions joined early-morning picket lines outside the two restaurants, while Labour leader Jeremy Corbyn offered his backing.
The workers are calling for a wage of at least £10 an hour and more secure working hours.
McDonald’s said those taking action represented 0.01% of its workforce, adding that the dispute was related to its internal grievance procedures.
BFAWU national president Ian Hodson, speaking from the picket line in Cambridge, said members of the public were offering their support to the workers.
“McDonald’s has had countless opportunities to resolve grievances by offering workers a fair wage and acceptable working conditions.
“For far too long, workers in fast food restaurants such as McDonald’s have had to deal with poor working conditions, drastic cuts to employee hours, and even bullying in the workplace - viewed by many as a punishment for joining a union,” he said.
Mr Corbyn said: “Our party offers support and solidarity to the brave McDonald’s workers, who are making history today.
“They are standing up for workers’ rights by leading the first ever strike at McDonald’s in the UK.
“Their demands - an end to zero-hours contracts by the end of the year, union recognition and a £10 per hour minimum wage - are just and should be met.”
McDonald’s, which employs around 85,000 staff in the UK and one million worldwide, announced in April that workers would be offered a choice of flexible or fixed contracts with minimum guaranteed hours, saying that 86% have chosen to stay on flexible contracts.
A company spokesman said: “We can confirm that, following a ballot process, the BFAWU has indicated that a small number of our people representing less than 0.01% of our workforce are intending to strike in two of our 1,270 UK restaurants.
“As per the terms of the ballot, the dispute is solely related to our internal grievance procedures and not concerning pay or contracts.
“As announced in April this year, together with our franchisees, we are providing our people with the option of a guaranteed hour contract, and all restaurants will have these contracts in place by the end of 2017.
“McDonald’s UK and its franchisees have delivered three pay rises since April 2016; this has increased the average hourly pay rate by 15%.
“We are proud of our people at McDonald’s, they are at the heart of all we do and we work hard to ensure that our teams are treated fairly. Our internal processes underpin that commitment.”
Around 40 workers were on strike and will later attend a rally in Westminster.