Cornish Pirates boss Chris Stirling says Cornwall must have a stadium if sport in the county is to progress.
The Pirates home at the Mennaye Field in Penzance is unsuitable for Premiership rugby.
The club, along with Truro City Football Club, are hoping to move to a planned new stadium at Threemilestone on the outskirts of Truro.
"Without it there won't be fully professional top-grade sport in Cornwall," he told BBC South West.
"At the moment we're the only fully professional sporting side but there's teams with aspirations."
Plans for the new stadium are being considered, with a feasibility study saying it could create up to 400 jobs.
Truro City chairman Kevin Heaney says without a stadium the club's meteoric rise up the leagues will come to a halt.
"Truro City is built on the grounds that it'll be the flagship football club for Cornwall, just like the Cornish Pirates are the flagship rugby team for Cornwall," Heaney told BBC Radio Cornwall.
"That's why we're building the community stadium. Unless that happens then you won't see a professional football team and ultimately a Premiership rugby team."
Truro have risen from local league football to the Blue Square Bet South over the past decade under the leadership of Heaney.
"The people of Cornwall have got to decide 'do we want the top flight sport?'", he added.
More than 11,000 people signed a petition supporting the plan for a community stadium, which would also have a business centre and commercial facilities.