Public sports facilities across Scotland are facing the threat of permanent closure as a result of the lockdown.
Charitable trusts which run services like gyms and swimming pools for councils have warned they are in a "perilous" financial position.
A letter obtained by BBC Good Morning Scotland outlines their fears.
Cosla said it is holding "detailed discussions" with the Scottish government over the impact of Covid-19.
Leisure facilities across Scotland have had no income since they were forced to close when the lockdown was introduced in March.
Some outdoor sports, such as golf and bowls, were allowed to resume at the end of May.
But gyms, swimming pools and indoor sports courts are not scheduled to reopen until 14 September.
The letter to Cosla from umbrella body Community Leisure UK highlights the devastating impact of the pandemic on the country's 27 charitable and leisure trusts.
In it, chairman Robin Strang warns: "The resulting loss in income has placed many trusts in a financially perilous position, with the very existence of many at imminent threat."
Mr Strang highlights a recent survey which found 38% of members will be non-viable or in an insecure position by the end of the year, growing to 70% inside 12 months.
It also reveals 450 contracted and casual staff have already been made redundant or planned for redundancy.
And it forecasts more than 4,500 jobs are at risk, with those aged 18-34 most affected.
June Peebles, chief executive of Edinburgh Leisure, told Good Morning Scotland: "Public leisure facilities throughout Scotland are facing huge financial challenges and it's fair to say that we are in crisis."
She also highlighted that when facilities re-open physical distancing means their income will be much lower than before.
Ms Peebles added: "Without financial support it is leaving swimming pools, gyms, libraries throughout the country just not viable and they are such vital public services.
"More than ever at the moment good health and well being is so important and that's what we deliver."
'Venues will close'
She added that about 900 of her staff remain on furlough and called on Cosla to deliver "urgent" financial support to help the struggling sector.
Edinburgh Leisure alone estimate the impact of the crisis over a 12-month period could be between £7m and £8m.
Ms Peebles said: "It is challenging for all of us but, without financial support, venues will close."
At the weekend Edinburgh Leisure confirmed that just three public pools in the capital will reopen when next month while seven will remain closed.
A Cosla spokesman said: "This is a confidential letter that was only sent to the Cosla president on Friday and we will respond to it in person rather than via the media.
"What I can say is that Cosla is in detailed discussions with the Scottish government in relation to the costs to the whole of local government as a result of Covid and the huge impact that is being felt across all of the services that we deliver both ourselves and with partners to communities across Scotland."