Workers at two branches of the American diner chain TGI Fridays are holding walk-outs over changes they say will cost them hundreds of pounds a month.
The firm has introduced a new pay policy, which redistributes customer tips from waiters to kitchen staff.
The 24-hour strike will affect branches in Milton Keynes and Covent Garden.
The Unite union has forecast a “summer of disruption” by unhappy employees. The firm said it pays its staff fairly and is working to find a resolution.
Flagging consumer spending on casual dining combined with rises in the minimum wage are squeezing profits at mid-market restaurants like TGI Fridays.
In February the chain introduced a system that takes 40% of tips paid by customers on credit and debit cards for redistribution to back-of-house staff.
Unite said the aim was to reduce staff turnover in kitchens by giving them a pay rise without increasing costs.
But the union said it would cost waiting staff on the minimum wage up to £250 a month in lost income.
Dave Turnbull from Unite said it wasn’t a question of waiting staff not wanting to share with their colleagues, but was about “greedy” owners who “no longer want to pay their hardworking staff anything above the bare minimum”.
TGI Fridays, owned by American private equity firm Sentinel, operates 83 restaurants across the UK.
Mr Turnbull said: “Unite is warning TGI Fridays of a summer of disruption if management don’t do the decent thing and sit down with us to find a sensible solution to this dispute.”
A TGI Fridays spokesman said: “We believe all our team members should be – and are – treated and paid fairly.”
The spokesman said the firm was working with staff to find a resolution and aimed to keep the restaurants operating as normal despite the walk-out.
Two years ago a government review of tipping practice advised that workers should retain all the tips given by the public. However there are no laws restricting restaurant practice and redistribution among non-waiting staff does not contravene best practice recommendations.
In March TGI Fridays was among 43 hospitality sector firms fined for failing to pay staff the National Minimum Wage. TGI Friday’s had to repay £25 each to 2,300 staff for the purchase of their black uniform shoes.