Some of Wales' biggest sports clubs and bodies have warned that they could go bankrupt if the Welsh Government does not provide clarity on how spectators can return safely.
The coronavirus pandemic means it has been more than eight months since fans were allowed into stadiums.
Clubs in certain areas of England were allowed to welcome a limited number of supporters into their stadiums from 2 December, when the four-week lockdown ended.
But senior representatives of elite rugby, football, cricket, horse racing and ice hockey clubs said current plans for Wales will effectively close them to the public indefinitely.
In an open letter to the First Minister, Steve Borley, Executive Director at Cardiff City Football Club, said: "Sport is a fundamental part of life in Wales.
"We form part of an an industry that employs thousands of people across the country, our contribution to the Welsh economy, employment and well-being is significant, but this is now at risk.
"The situation is grave; the lack of a clear roadmap for the return of spectators in Wales poses the real risk of bankruptcy for our sports."
The letter was signed by top bosses at the Welsh Rugby Union, the Football Association of Wales, Glamorgan Cricket Club, Swansea City FC, Newport County, Dragons Rugby, Scarlets Rugby, Ospreys Rugby, Chepstow and Ffos Las Racecourse, Bangor on Dee Races, Wrexham FC and Cardiff Devils.
Following a recent consultation on the return of fans to Welsh stadiums, the sporting executives said they were "extremely disappointed" by the Welsh Government's position.
The UK Government allowed the phased return of spectators in England after the Sports Grounds Safety Authority (SGSA) published guidance, titled 'SG02', that worked on the basis of fans keeping a one metre distance from each other.
But the Welsh Government has requested guidance based on social distancing of two metres, which sporting bodies have warned would pose dire consequences.
"SG02 reduces expected attendances to between 25 per cent and 35 per cent of capacity depending on concourse densities and stadium layouts," Mr Borley continued.
"The Welsh version would further reduce capacity to under 10 per cent - a level which, in effect, closes our businesses to the public indefinitely."
In areas of England placed under Tier 1 - where Covid rates are lowest - the crowd size at outdoor venues is restricted to 50 per cent of capacity or to 4,000 spectators, whichever is smaller.
In Tier 2, 50 per cent of outdoor venues or 2,000 spectators are allowed in, whichever is smaller.
Crowds at indoor sport venues are restricted to a maximum of 1,000 spectators in both tiers.
The Welsh clubs have called on the First Minister to follow the same guidance adopted by the UK Government, and "to produce a clear roadmap for meaningful pilot test events and the safe return of fans to sporting grounds and events".
Mr Borley added: "We respect the need to return when it is safe to do so and acknowledge the need to follow science, yet highlight the reluctance of Welsh Government to look at a 'managed and engineered solution' not present in the retail, construction, transport or hospitality sectors.
"You will also be very conscious that Welsh sports fans are watching what is happening over the border.
"For a nation that is small in size, Wales punches well above its weight in sporting terms; we want to work with Welsh Government to ensure the survival of our people, clubs, businesses and the future of sport in Wales."
The Welsh Government said full capacity events are unlikely to restart before spring next year, but that it is considering test events in February.
"Our approach to easing restrictions is always in the context of the public health conditions and as cases of coronavirus accelerate in Wales and erode the gains made through the firebreak, we are strengthening the national measures in place in Wales," a spokesperson said.
"The longer term position is more optimistic with vaccines and fast-track testing likely to provide additional tools to facilitate the safe return of fans to sports grounds."