The Welsh Government has bought a 3% stake in the sports car maker TVR for £500,000.
It has also provided a £2m loan to the company ahead of production getting underway in Ebbw Vale.
TVR said there is another year of research to be completed before manufacturing is due to begin in 2019.
The Tories called for assurances that public money is being safeguarded. The Welsh Government said it will ensure taxpayers benefit from future success.
The site where TVR plans to produce its new cars was acquired by the Welsh Government last year.
The 200,000 sq ft former Techboard building is part of plans to invest £100m by ministers in an automotive business park in Ebbw Vale.
The TVR brand was bought by new owners in 2013 after the company had stopped production more than a decade ago in Blackpool.
The firm now plans to create 150 jobs in Ebbw Vale.
A Welsh Government spokesperson said: "TVR are making good progress with their new car and have secured all necessary funding to complete the pre-production design and engineering development work.
"As part of our initial support package to commit TVR to manufacturing in Wales and following independent and specialist due diligence, we provided a repayable commercial loan to the company in early 2016. This was made alongside a private sector lender.
"At the same time Welsh Government also invested £500k into equity on the same terms as other investors.
"This gives the Welsh Government a minority stake of just below 3% that will ensure the Welsh tax payer benefits from the company's successes."
The Welsh Conservatives called for assurances from ministers that taxpayer money is being properly safeguarded.
Economy spokesman Russell George said: "We need to see tangible evidence that this investment represents value for money.
"The prestige of the TVR badge is one thing - and there is understandable excitement around their decision to locate in Wales.
"However, we need to see the jobs that were promised, and as major shareholders in the company the Welsh public will want to see genuine progress.
"Millions of pounds have been invested in TVR, and the Welsh Government must ensure that this exciting project doesn't turn into another disappointment for the people of Blaenau Gwent."