The online fashion seller Shein has refused to reassure British MPs that its products do not include cotton produced in the Xinjiang region of China, which has been linked to forced Uyghur labour, prompting one MP to accuse its representative of “wilful ignorance”.

In testy exchanges before MPs on the business and trade committee, Yinan Zhu, the general counsel for Shein’s European arm, repeatedly said she was not qualified to answer questions about the fast-fashion retailer’s supply chain amid concerns from campaigners over forced labour.

Zhu said she could not answer questions about whether Shein’s manufacturers – none of which the company owns directly – used the controversial yarn or whether any of them were based in the Xinjiang region. She said the company may be able to provide a written answer in future.

Zhu was sent a dossier outlining links between cotton production in the region and forced labour of the Muslim minority Uyghur people.

However, she said the material, put together by the campaign group Stop Uyghur Genocide, was “not specifically relating to Shein”, which is headquartered in Singapore but founded in China where most of its products are made.

She said Shein, which is believed to be hoping to list on the London Stock Exchange this year – valued at as much as £50bn – was confident that the company met all UK laws including modern slavery rules.

Shein had initially planned to list in New York but reportedly decided on London after opposition from US politicians. Last summer, Labour indicated its support for Shein’s potential London listing.

Zhu said on Tuesday that independent auditors carried out thousands of checks on its suppliers and that any found using forced or child labour would have their contracts “immediately terminated”.

However, Zhu could not list the 140 categories suppliers were checked against or say if a ban on Xinjiang cotton was among them.

The MP Charlie Maynard said politicians had “asked very simple questions”, such as whether Shein products contained any cotton from China, and Zhu was “not giving us straight answers” and was displaying “wilful ignorance”.

He said Zhu had been “unhelpful and disrespectful”, being “blatantly void of answers”, adding: “You have obfuscated wilfully.”

Liam Byrne, the chair of the committee, added: “For a company seeking to float on the London Stock Exchange, the committee has been pretty horrified by the lack of evidence.”

He said MPs had been given “almost zero confidence” by Shein on where products were made or the conditions for workers in its supply chain.

However, he welcomed “some reassurance” from Shein’s rival Temu.

Stephen Heary from the Chinese-owned online marketplace, said it had “taken on board feedback from stakeholders and consumers” and did not permit sellers from the Xinjiang region to sell products on the site.

However, he did not say whether the company had banned the use of cotton from the region.