British online fashion retailer Boohoo on Wednesday denied allegations that staff in a UK warehouse worked in harrowing and health-threatening conditions and regarded themselves as "slaves".

The Times newspaper, in an undercover investigation, reported that workers at Boohoo's facility in Burnley, northwest England, complained of racism, sexual harassment, poor safety equipment, inadequate training and "gruelling" targets.

However, a Boohoo spokesperson said that it "does not believe the picture painted is reflective of the working environment at our Burnley warehouse".

Boohoo "is taking every claim very seriously", the spokesperson said, adding that making sure workers are safe and comfortable is the company's "highest priority".

The Times, whose undercover reporter worked at the warehouse for one month, said each staff member walked the equivalent of a half-marathon (13 miles, 21 kilometres) per shift.

Night-time summer temperatures reached up to 32 degrees Celsius (89.6 degrees Fahrenheit) and frequently collapsed, it alleged.

The daily added that Burnley employees are paid £11 ($13.25) per hour in shifts that are up to 12 hours long.

Each staffer must fetch 130 items every hour, it said.

The online retail group has annual sales of almost £2.0 billion per year, and its chief executive was paid a £1.3 million bonus this year.

Boohoo had already been rocked last year by allegations that one of its suppliers in Leicester, central England, paid workers much less than the national minimum wage.

The group's suppliers were meanwhile accused also of underpaying staff in Pakistan.

Boohoo benefited from an online sales boom during the pandemic, during which it expanded aggressively to snap up brands belonging to collapsed UK retail giants.

It bought fashion labels Burton, Wallis and Dorothy Perkins from Arcadia, as well as assets of failed UK department store Debenhams.

The company employs about 5,000 people worldwide, according to its website.