Food delivery company Deliveroo's new proposed pay deal for workers marks a return to Victorian Britain, Labour has said.
Shadow business secretary Jon Trickett attacked the firm's reported plans to introduce a pay-per-delivery scheme, which will replace the existing pay-per-hour deal next week.
Hundreds of its workers protested in London on Thursday over the reported plans to pay them £3.75 per delivery rather than the current terms of £7 an hour and £1 per delivery.
The company delivers food from thousands of restaurants which do not have their own delivery service and counts the likes of Pizza Express, Byron burgers and Gourmet Burger Kitchen among its clients.
It charges customers £2.50 per delivery for its service.
Mr Trickett said he backed the Deliveroo riders in their protest.
"Deliveroo workers are right to demand proper pay and conditions," he said.
"The company is offering a return to a Victorian system which has no place in modern Britain.
"Flexible working may suit some workers who have domestic or other commitments, but it should not be used as an excuse by employers to cut costs and increase employees' insecurity.
"After all, rent, fuel bills and food costs don't vary week to week so nor should incomes purely to suit the employer.
"Equally, 21st century employers ought to recognise that the best way to build a successful and competitive enterprise is in part to create harmonious industrial relations by recognising the right of employees to join a trades union.
"Labour will take action in government to end exploitative employment practices."
Deliveroo insisted the plans were a trial in certain areas of London with around 280 riders taking part, out of more than 3,000 in the capital.
In a blog post, it said pilots of the pay-per-delivery system have led to a doubling of average hourly fees for riders during the busiest times.
Deliveroo's UK & Ireland managing director Dan Warne said: "We want to be clear that this is a trial happening in certain parts of London.
"We are engaging with riders who work within those trial areas to get their feedback and listen to their concerns.
"We're committed to having an open conversation about our trial, our payment model and delivery experience for riders".