The German chemicals producer BASF “appears to be implicated in gross abuses” of Uyghurs in Xinjiang and should withdraw from the Chinese province, a group of politicians from around the world have said.

The group made the allegation in a letter to BASF’s chair, Martin Brudermüller, on Monday, after the German media outlets Der Spiegel and ZDF published a joint investigation on Friday.

The investigation found that in 2018 and 2019 people employed by BASF’s Chinese partner company, Xinjiang Markor Chemical Industry, in Xinjiang accompanied Chinese state officials on home visits to Uyghur households, as part of a government initiative that human rights groups have said is used to spy on people and indoctrinate them.

The visits were part of the fanghuiju campaign, in which officials from government agencies, state-owned enterprises and public institutions in Xinjiang visit Uyghurs and other minorities at home to collect information and monitor people’s behaviour.

Human Rights Watch has described fanghuiju visits as invasive and said that “families are required to provide officials with information about their lives and political views, and are subjected to political indoctrination”.