Toyota bosses were warned about the safety implications of their aggressive cost-cutting as long ago as 2006, according to evidence submitted to the US Congress yesterday.

A letter sent to former chief executive Katsuaki Watanabe from a minority labour union warned safety was being compromised in favour of competitiveness.

The memo — whose principal author, Tadao Wakatsuki, has worked at one of the company's factories for 45 years — singled out Toyota's reduced product development times, the pressure heaped on suppliers to cut component prices, and the increased use of computerised safety testing. It also criticised ‘amateurism’ in the production process thanks to the mass-hiring of short term contractors, and warned that the problems could ultimately threaten the firm's survival.

The warning appears strikingly prescient as Toyota struggles to withstand the reputational damage of recalling 8.5m vehicles in recent months following a string of technical problems including sticky accelerator pedals and issues with braking systems.

The letter was put together by the All Toyota Labour Union (ATLU), a group which was started by Mr Wakatsuki in 2006.

The revelations came alongside news that Daihatsu, which is 51% owned by Toyota, is recalling nearly 275,000 of its Hijet and Atrai vehicles in Japan over issues including missing or loose suspension bolts, loose fuel hoses and defective brake lights.