The Welsh Government has spent more than £11m on Parc Bryn Cegin business park in Bangor, which has remained empty for 20 years.
The business park opened in 1999 following a consultation that suggested it was needed.
Senedd member Siân Gwenllian has now called the matter “a scandal” and she has called for an independent investigation into the spending.
The Welsh Government said it was working with Gwynedd Council to “attract businesses to the site.”
The figures came to light following a BBC Wales Freedom of Information about the site.
The Welsh Government did not comment on what the money had been spent on.
Siân Gwenllian said: “It is absolutely unacceptable that so much money has been spent on this site and yet there is nothing – nothing – to be seen there in terms of any jobs of any kind.
“I don’t know what has gone wrong, and I think we need an investigation into that. Is it that that is not a priority for the Welsh Government?
“I simply don’t know, but I do know that it is scandalous”.
Ms Gwenllian hoped the site would be used to stimulate the local economy following Covid-19’s effects.
There was a need for “high quality jobs” in the area, she said.
The site was advertised as being able to host up to 1,600 jobs over a 70,000 sq m site. However there are no businesses are trading there.
About £3.5m of the £11.37m spent came from the European Union, while £4.9m of it came from the Welsh Development Agency.
The site is part of the North Wales Growth Deal – which aims to create thousands of jobs in Wales.
The North Wales Economic Ambition Board, responsible for handling the North Wales Growth Deal, said it was “aware of the potential for employment and business growth” and was “working with partners”.
Gwynedd Council said part of the land is being used for a park-and-ride scheme.
Report: BBC
