A UK-based conglomerate and a plantation owner in Malawi which supplies some of Britain's biggest tea brands are being sued in London over allegations of rampant sexual violence against female workers.

British legal firm Leigh Day said on Sunday that it wanted financial redress for the women from their Malawi employer, Lujeri Tea Estates, and its British parent company PGI Group Ltd.

The complaint filed in London's High Court says women harvesting tea and macadamia nuts for Lujeri in southern Malawi were subject to at least 10 instances of rape and other violence at the hands of male supervisors.

One 39-year-old mother of two began to be sexually harassed by a supervisor soon after she started work for Lujeri as a macadamia picker in early 2018, and her pay was docked when she refused his demands, according to Leigh Day.

"After several more weeks of harassment, the supervisor raped the claimant and she became pregnant as a result, and later gave birth to a stillborn son in December 2019," it said.

In the lawsuit, Leigh Day argues that PGI Group and Lujeri were negligent in their duty of care towards the female employees.

There was no immediate response by PGI.

In a statement, Lujeri in Malawi said it was "deeply troubled" by the allegations and had launched disciplinary proceedings against 25 employees after finding "clear evidence of misconduct".

Lujeri supplies tea to well-known British brands including Tetley, Typhoo and PG Tips
Lujeri supplies tea to well-known British brands including Tetley, Typhoo and PG Tips AFP / Tolga AKMEN

The company's managing director, Grant Bramsen, said changes had already been made to combat abuses following a critical report in 2016 by the charity Oxfam into the state of Malawi's tea industry.

"Clearly, they did not go far enough," Bramsen said, vowing to implement new recommendations made by an outside trade consultancy "to the letter".

"Our buyers are aware of these allegations and are in support of the measures that the Tea Estates are putting in place," he added.

Lujeri supplies tea to well-known British brands including Tetley, Typhoo and PG Tips, as well as the own-brand tea labels of top supermarkets.

All the British companies involved are looking into the claims and several have suspended ties to Lujeri, the Sunday Times newspaper reported.

Two of the tea brands supplied by Lujeri -- PG Tips and Lipton -- are owned by consumer goods giant Unilever, which said that any abuse of workers was "unacceptable".

Unilever will "continue to work with industry groups and partners to help the Malawi tea industry improve the lives of tea workers and bring an end to sexual and gender-based violence", a UK spokesperson told AFP.

In February, Leigh Day won a settlement worth ?6.9 million ($9.5 million, 8.1 million euros) from UK-based food supplier Camellia over similar allegations at farms in Kenya and Malawi.

The latest case could ultimately go to trial, but Leigh Day partner Sapna Malik indicated the same outcome as February would be preferable.

"A satisfactory financial settlement would be a good outcome as well as the implementation of changes to working practices in the Lujeri plantations," she told AFP.