TAIPEI - A senior lawmaker of Taiwan's ruling party thanked major submarine producing nations on Tuesday for helping with the island's submarine programme, after Reuters reported on the multinational effort.

Taiwan, claimed by China as its own territory, has made the indigenous programme a key platform of an ambitious project to modernise its armed forces as Beijing steps up military threats against the democratically-ruled island.

The Reuters investigation showed firms in Britain, the United States and Canada helped with the submarines, while Taiwan succeeded in hiring engineers, technicians and former naval officers from at least six nations: Britain, Australia, South Korea, India, Spain and Canada.

The submarine programme was "continuing to progress", Tsai Shih-ying, secretary-general of the legislative caucus of the Democratic Progressive Party (DPP) told reporters in response to the report.

"Thank you to the world's major submarine producing countries for helping Taiwan," he added, but did not identify any. "No matter how many countries it is, many, many thanks."

Later, he told Reuters of his concern that China might try to stymie the plan.

"In the entire project, the most difficult problem is that China can put pressure through various channels. Honestly speaking, China has never given up on these efforts," Tsai said, but did not elaborate.

"I hope China will not interfere with the development of Taiwan's submarines."

China's Taiwan Affairs Office did not immediately respond to a request for comment.

In response to the Reuters investigation, a spokesperson for China's foreign ministry said Taiwan "authorities are colluding with external forces" on the program, and the countries concerned should refrain from participating in the effort.

State-backed shipbuilder CSBC Corp Taiwan began construction last year and aims to deliver the first of the planned eight vessels by 2025, the government has said.

Taiwan now has four ageing submarines in service, two dating from World War Two, in a fleet that is dwarfed by China's.