China protests "gross interference" in its internal affairs by a group of British legislators visiting Taiwan, and has vowed a very harsh response to any actions that jeopardize Chinese interests.
According to a representative, the visit sent the wrong message to people who support Taiwan's independence.
In a statement in response to the current trip to Taiwan by the British parliament's Foreign Affairs committee, the Chinese embassy in Britain referred to it as a "flagrant violation" of the one-China principle.
"The Chinese side urges the U.K. side to abide by its commitment, stop any actions that violate the one-China principle, and stop interfering in China's internal affairs," the spokesperson said in a statement posted on Twitter.
"Moves of the U.K. side that undermine China's interests will be met with forceful responses from the Chinese side."
As part of its "one China" policy, China claims the self-governed, democratic island of Taiwan as its own territory. Taiwan's government opposes China's claims to sovereignty.
On Thursday, the committee met with Taiwan's Premier Su Tseng-chang, and will meet with President Tsai Ing-Wen on Friday.
The visit is part of the committee's assessment of a change in British foreign policy toward the Indo-Pacific region, which the government has highlighted as an economic and diplomatic priority since Britain's exit from the European Union.
The committee is a parliamentary body apart from the government, comprised of elected members from various parties. It examines government policies but lacks statutory authority.
Taiwan sees Britain as a democratic partner who shares its values, so it has been encouraged by London's worries about recent Chinese war games near the island and by its support for Taiwan's membership in international organizations, the majority of which Taiwan is barred from joining because of China's objections.
The Comprehensive and Progressive Agreement for Trans-Pacific Partnership, or CPTPP, is being sought by both Taiwan and Britain. In February, members decided that Britain may move through with its application as it seeks new economic partners after leaving the EU.
Although there are no formal diplomatic relations between Britain and Taiwan, there are strong informal and commercial ties between the two countries, and Britain keeps a de facto embassy there.
Chinese Foreign Ministry spokesman Zhao Lijian said in Beijing that China is adamantly opposed to any type of official exchange between a country with which it has diplomatic ties and Taiwan.
Western MPs and other officials have increased their visits to Taiwan, despite Beijing's strong opposition, which regards the island as its own territory and objects to any suggestion that it is a separate country.