TAIPEI--Concerns a Taiwan bird group was bent on promoting the Chinese-claimed island’s independence drove a British charity to ditch ties with them, according to letters published on Friday, as a complex geopolitical tangle entered the world of conservation.

Taiwan’s Chinese Wild Bird Federation (CWBF), since renamed the Taiwan Wild Bird Federation (TWBF), this month became the latest and unlikely frontline in Chinese efforts to assert sovereignty over the democratically-ruled island.

China has ramped up pressure on international groups and companies to refer to Taiwan as being part of China, to the anger of Taiwan’s government and many of its people.

In correspondence published by the TWFB on its website, the Cambridge-based BirdLife International said it was committed to “follow UN positions and protocols on countries and territories” and to treating Taiwan, which it referred to as “Chinese Taiwan,” as part of China.

BirdLife, which said it was responding to an internal risk review, demanded the group stop using the expression Republic of China, Taiwan’s formal name, “and/or any other expression suggesting independence.”

It also asked them to formally commit not to advocate or promote in any way Taiwan’s independence of Taiwan or the legitimacy of the Republic of China.

It is not clear from the correspondence whether the Chinese government was involved in the request, though expressions like “Chinese Taiwan” are how Beijing requires international organizations refer to the island.

BirdLife did not respond to several requests for comment.

The TWBF, which had refused to sign any political documents, reiterated it has never taken a political position.

“We are conservationists, not political actors. In fact, it was BirdLife who asked us to take a political stance by insisting we sign an overtly political declaration and by describing us as a ‘risk,’ without ever clearly defining what that risk was.”

Beijing’s government took over the Chinese seat at the United Nations in 1971 from Taipei, though the U.N. resolution on that move makes no explicit mention of Taiwan’s status.