Online retailers Shein and Temu are facing increased pressure in the US after two senior politicians pushed for investigations, including into claims of forced labour and intellectual property (IP) theft.

In Texas, the state's Attorney General Ken Paxton launched a probe into allegations of forced labour and the use of unsafe materials at Shein.

At a national level, Senator Tom Cotton called for a federal investigation into possible IP theft at both Shein and Temu, which he labelled "Communist Chinese" platforms.

Shein said it took concerns raised about its business practices seriously. Temu did not immediately respond for comment.

Shein said in a statement that it would cooperate with the investigation and that it welcomed "constructive engagement" with Paxton.

It said in response to Cotton's letter that the company continues to invest in protecting the rights of designers worldwide.

"We are constantly improving our internal processes to better protect creators," said Shein.

The retailer is headquartered in Singapore, but most of the goods sold on its platform are made in China, where it was founded.

In a letter to US Attorney General Pam Bondi on Monday, Cotton - senior Republican from Arkansas- said that millions of packages from China now sit in US warehouses after Washington changed its rules on low-cost shipments in August.

US President Donald Trump abolished the longstanding de minimis rule, a global tariff exemption widely used by buyers of low-cost goods.

The change subjected shipments to levies and stricter customs checks.

The new regulations gives the Department of Justice and Homeland Security a "golden opportunity" to act, said Cotton, a key ally of Trump and a vocal critic of China.

Designers and small American brands have accused Shein of systematically copying their original creations, often just days after launch, and selling them at a fraction of the price, he said.

Cotton also accused Temu of carrying "sophisticated and deceptive fakes" on its platform, which has hundreds of millions of users.

Cotton cited a US investigation which found a significant proportion of items that its researchers bought on Shein and Temu were likely counterfeits.

Separately, Paxton from Texas said that numerous reports have raised serious concerns about Shein's alleged reliance on forced labour, and claims of the use of unsafe materials and deceptive marketing.

The brand has been under scrutiny over the environmental impact of its fast-fashion business and the working conditions of the people who make the products on its site.

The Republican lawyer said the investigation will assess if Shein's practices violate Texas law by allegedly using hazardous materials and if it has misled consumers about ethical sourcing. The probe will also examine Shein's data collection practices, he added.

"I will not allow cheap, dangerous, foreign goods to flood America and jeopardise our health," said Paxton online.

Shein also faces calls by the European Union to curb sales of childlike sex dolls and weapons on its third-party marketplace place after French authorities flagged the products in November.

Temu is also being investigated in France over the spread of harmful content accessible to young people.

Shein is not the only firm under fire by Paxton, who, like Cotton, is a close ally of US President Donald Trump. He sued Roblox in November for "flagrantly ignoring" safety laws and deceiving parents about the dangers that the platform is said to pose to young gamers.

Roblox has denied the claims, which it said are based on "misrepresentations" of its online gaming platform.