British online fast fashion retailer Boohoo has been accused of pressurising its suppliers to slash prices, an investigation by BBC Panorama has revealed.

A BBC reporter, Emma Lowther, went undercover for ten weeks at the retailer’s head office in Manchester.

In her role as an admin assistant, the reporter saw suppliers facing shorter deadlines and staff pressuring suppliers to drive prices down, even after deals had been agreed.

The reporter also saw the company’s staff were under "constant pressure to drive down prices” even further.

Boohoo reportedly defended its treatment of suppliers, citing cost inflation.

A spokesperson of Boohoo was quoted by Reuters as saying: "Like all businesses, we have experienced significant cost inflation over the last year, which we have absorbed in order to maintain affordable prices for customers.

"As the cost of raw materials, freight and energy started to come down, the Group asked its suppliers to reflect this in their pricing through discounts of between 1% and 10%, and we passed the savings onto customers.”

Following BBC’s revelation, the Union of Shop, Distributive and Allied Workers (Usdaw) urged Boohoo to "clean up" its supply chain.

The workers' union also called for the retailer to treat their staff with fairness and respect.

Usdaw regional secretary Mike Aylward said: “We have yet again asked Boohoo to take the simple step of sitting down with Usdaw to explore how we can work together. Staff, the local community, councillors, MPs and campaign organisations all want this to happen, to help make Boohoo an ethical trader.

 “The company could go a long way towards repairing their damaged reputation by meeting with Usdaw and engaging in a positive relationship. Regrettably, we have still received no response; for the sake of their employees we hope that will change.”

The report comes three years after Boohoo promised to overhaul its business practices and launched its "Agenda for Change" programme.