TAIPEI, May 17 (Reuters) - Former British prime minister Liz Truss will say in Taiwan on Wednesday (May 17) that the West must avoid appeasing China and show unwavering support for the self-governed island, in a speech that risks further damaging Britain's relations with Beijing.

Truss is the most well-known British politician to visit Taiwan since former prime minister Margaret Thatcher in the 1990s, and her trip comes at a time when relations between Britain and China are the worst in decades.

She represents a hawkish wing of the governing Conservative Party that opposes the British government's approach to China, which involves seeking to engage in areas such as trade and climate change while trying to limit national security threats.

In contrast to French President Emmanuel Macron's attempts to distance Europe from any involvement in a conflict over Taiwan, Truss will say it would be "completely irresponsible" for European nations to argue that the island is too far away or not important.

China claims Taiwan as its own and has not renounced the use of force to ensure eventual unification. Beijing has previously condemned visits by British lawmakers to Taiwan for what it calls interference in China's internal affairs.

"We must support free democracies like Taiwan in the face of aggression from a Chinese regime whose record is all too clear for the world to see," Truss will say, according to extracts of her speech. "The only choice we have is whether we appease and accommodate - or we take action to prevent conflict."

After being forced out of office in a record 49 days last October over unfunded tax cuts that buffeted the financial markets, Truss has made speeches aimed at rebuilding her political reputation and adding pressure on her successor, Rishi Sunak, to take a stronger stance on a number of issues.

A spokesperson for the Chinese Embassy in London criticised her visit, calling it a "dangerous political show which will do nothing but harm to the United Kingdom".

In the clearest attempt to explain Britain's approach to China under Sunak, the foreign minister James Cleverly said last month it would be a mistake to isolate Beijing and that engagement is needed in areas such as climate change.

"There are still too many in the West who are trying to cling on to the idea that we can cooperate with China on issues like climate change," Truss will say. "Without freedom and democracy there is nothing else."