Britain’s House of Commons foreign affairs committee is planning a visit to Taiwan later this year – probably in November or early December – despite rising tensions in the region, the Guardian has learned.

Sources say the trip – which was originally scheduled for early this year but was postponed due to one member of the delegation testing positive for Covid – was intended to show Britain’s support for the democratically run island, which China considers its own.

It comes as London’s relationship with Beijing continues to deteriorate. Last week, the Conservative leadership candidates, Liz Truss and Rishi Sunak, articulated their tough positions on China. And China’s ambassador to the UK accused some British politicians of “peddling the fallacy of the so-called China threat” in a video remark.

Tensions have been rising in the Taiwan strait in recent weeks after reports of a possible trip to Taipei by the US House speaker, Nancy Pelosi. Beijing has repeatedly warned against such a move and has threatened to take “decisive actions” if the trip goes ahead. Pelosi is now on a trip to Asia, where she has scheduled stops in Singapore, Malaysia, Japan and South Korea.

On Saturday, China’s People’s Liberation Army (PLA) conducted “live-fire exercises” near Pingtan island off Fujian province, according to the official Xinhua news agency. China’s maritime safety administration warned ships to avoid the area. The drills also came ahead of the 1 August PLA founding anniversary.

During their fifth phone call last week, China’s president, Xi Jinping, warned the US president, Joe Biden, not to “play with fire” over Taiwan. On Monday, China’s spokesperson said its military would “not sit idly by” if Pelosi went ahead with the Taiwan trip.

Tom Tugendhat, who chairs the foreign affairs select committee, is expected to lead the delegation to Taiwan later this year. But as he extended his backing to Truss over the weekend, there was speculation he may be given a cabinet-level job in her administration if she wins the race in September. But even if this happened, one source said, the trip would go ahead “whoever becomes the next chair”.

It is unclear whether the British delegation would meet Taiwan’s president, Tsai Ing-wen. Details of the trip are being hammered out, including the dates of the visit, sources have suggested. In the past, the Taiwanese leader has personally welcomed delegations from the European parliament and members of the US and Czech senates.

The move is yet another sign that London is strengthening its ties with Taiwan as it now regards China as a long-term threat to the UK. Officially, Britain continues to stick to its “one-China policy”, which recognises Beijing as the sole legal government of China, but it keeps ties with Taiwan on an unofficial level.

Truss, the foreign secretary, has in recent months urged western countries to ensure Taiwan can protect itself from China. In June, she remarked in an interview that the UK should provide Taiwan with weapons – a comment that surprised some of her fellow MPs and colleagues, the Guardian understands.

The Taipei representative office in London declined to comment on details of the potential visit when approached by the Guardian, but it said Taiwan “welcomes any opportunities to strengthen its relations with Britain, including through visits from the UK”.

The foreign affairs committee said it “has had a longstanding intention to visit Taiwan, within the context of its inquiry into the tilt to the Indo-Pacific”. But it declined to comment on the details of the visit “due to security concerns and in line with normal practice”.