The Irish Rugby Football Union faces losing up to 20m euros if no more international rugby is played in 2020.
Chief executive Philip Browne said on Friday that the IRFU's cash reserves would be exhausted within months and that the club game "will take a generation to get back on its feet" without assistance from the government.
It is hoped the professional game in Ireland will resume in August.
Ireland's 2020 Six Nations campaign was suspended with two games left to play.
Unions hope the fixtures - against Italy and France - will be completed in October or November, possibly alongside other games scheduled for the autumn international series.
If the games go ahead behind closed doors, the IRFU still expects to lose between 10-15m euros this year.
Furthermore, a cancellation of next year's competition could result in the body losing 30m euros.
Browne called on the government to provide more financial support for sport as the Republic of Ireland and Northern Ireland begin to slowly emerge from their lockdowns.
Full contact sports are among the last things to return under government roadmaps, adding to the industry's financial concerns.
"We have hit a revenue cliff - there is no revenue coming into the provinces," said Browne, who added that the grassroots level was largely funded through the professional game.
"What we have to do is get back to competitive, revenue-generating matches as soon as we can."