LONDON (Reuters) - Online fast-fashion platforms Shein and Temu are gearing up for a 2026 trial at London's High Court, with the rivals trading allegations of copyright infringement and anti-competitive behaviour in competing lawsuits.

Shein sued Temu in Britain last year, accusing Whaleco UK Limited - whose ultimate parent is Temu's owner PDD Holdings ( PDD ) - of breach of copyright in relation to photos of some products available on the Temu platform.

Temu hit back with a counterclaim in February, accusing Shein of breaking British competition law by tying suppliers of fast-fashion products to exclusive agreements, a claim it values at 4.2 million pounds ($5.5 million) and which Shein denies.

Temu's lawyers said in court documents for a preliminary hearing on Tuesday that Shein is "flooding Temu with unwarranted notices of copyright infringement, disrupting the sale of products".

Their cases at London's High Court are expected to come to trial towards the end of 2026, Shein's lawyers said in court documents.

The London lawsuit is one leg of a global legal battle between the two rivals. Temu sued Shein in the U.S. in December, with Shein filing its own case against Temu in August.

Both Shein and Temu have rapidly expanded in international markets with low-cost clothing, accessories and gadgets, though they have come under increased scrutiny.

Shein has faced questions over its treatment of workers and environmental record, particularly ahead of a potential London listing. It has previously said it is committed to respecting human rights and has a zero-tolerance policy for forced labour.

Temu, meanwhile, is facing an investigation from the European Commission over whether it may have breached rules aimed at preventing the sale of illegal products. Temu has said it will cooperate with regulators.