China's embassy in the United Kingdom has urged British politicians to "strictly observe the one-China principle" and "not to underestimate the extreme sensitivity of the Taiwan question", following the UK foreign secretary's remarks in light of US House Speaker Nancy Pelosi's visit to China's Taiwan region.

"The one-China principle is a red line. It is also the political foundation and premise for the establishment and development of the diplomatic relations between China and the UK," the embassy's spokesperson said.

"We urge the UK politicians not to underestimate the extreme sensitivity of the Taiwan question, strictly observe the one-China principle, avoid being led astray by the US, stop making wrong remarks related to Taiwan, stop interfering in China's internal affairs, and stop sending wrong signals in any form to secessionist forces seeking 'Taiwan independence'."

Liz Truss, the UK's foreign secretary and one of two finalists in the election of Conservative Party head to be the UK's next prime minister, had previously clamored for helping Taiwan to defend itself from the mainland. During a campaign in Ludlow town on Wednesday, Truss accused China of using "inflammatory language" on Pelosi's visit and urged China "to de-escalate".

"Pelosi's visit to Taiwan, in brazen disregard of the firm opposition from the Chinese side, seriously violated the one-China principle and the provisions of the three Sino-US joint communiques, seriously infringed on China's sovereignty and territorial integrity, and seriously undermined peace and stability across the Taiwan Straits. We strongly condemn such a move," the spokesperson said.

'Inalienable part'

"Taiwan is an inalienable part of the Chinese territory. The Chinese people are firmly resolved to uphold national sovereignty and territorial integrity. The Chinese side will take firm and forceful measures to safeguard its core interests. The US side must bear full responsibility for the consequences of its wrongdoing."

Earlier this week, Zheng Zeguang, China's ambassador to the UK, said the anti-China rhetoric by certain UK politicians is "unfounded, very destructive and poisonous", and it has created uncertainties and unease among business communities and also in society.

"China and the UK have every reason to maintain close, productive and constructive relationship. It is in the interest of both countries and the world," Zheng said.

"We urge those UK politicians to stop making up stories, stop spreading the fallacy of the so-called 'China threat', and be realistic about the fundamentals of the relationship. They should stop spoiling, undermining China-UK relations."