China's UK ambassador Zheng Zeguang vowed "severe consequences" if British lawmakers visit Taiwan, the Guardian reported on Tuesday.
Visits would interfere in China's internal affairs and would lead to severe consequences in China-UK relations, Zheng said at a news conference in London, the report said.
"We call on the UK side to abide by the Sino-UK joint communique and not to underestimate the extreme sensitivity of the Taiwan issue, and not to follow the US's footsteps," the Guardian quoted Zheng as saying.
Zheng's comments came after the Guardian reported on Monday that Britain's House of Commons' Foreign Affairs Committee is planning a visit to Taiwan probably in November or early December this year.
Taiwan faces mounting pressure from China, which considers the democratically governed island its own territory.
Separately, tensions have escalated in the Taiwan Strait after the US House of Representatives Speaker Nancy Pelosi arrived in the Chinese-claimed self-ruled island late on Tuesday, a move that China condemned as a threat to peace and stability.
The committee did not immediately respond to a Reuters request for comment regarding Zheng's statement. Taiwan's Foreign Ministry office could not immediately be reached.
The reports come following a deteriorating relationship between China and Britain, with UK leadership candidates Liz Truss and Rishi Sunak demonstrating their tough stance on China as they race to replace Boris Johnson as Britain's next prime minister.
Responding to remarks about China by Sunak and Truss, Zheng urged British politicians to "be realistic" about the fundamentals of bilateral relations, the Guardian reported.