La Liga president Javier Tebas and Premier League chief executive Richard Masters have said their respective leagues could lose billions because of the indefinite postponement of the season due to the coronavirus pandemic.
Masters made his claim in a letter to parliamentary sports committee chairman Julian Knight in which he defended clubs furloughing staff using the government job retention scheme.
He said: "We face a £1 billion loss, at least, if we fail to complete season 2019-20, and further losses going forward if the seriousness of the pandemic deepens and extends into the future.
"This would negatively impact not only the finances of the 20 Premier League clubs, but would also have a significant detrimental effect across the whole professional football landscape. For this reason, clubs unanimously agreed to advance funds to the EFL and National League.
"Premier League club finances are dependent upon the receipt of money from broadcast rights sales, distributed by the Premier League, as well as revenues generated by each club from matchday income and commercial sponsorships. With no matches being played these resources have been temporarily halted, therefore clubs, like much of the UK's economy, are facing tough decisions in relation to protecting their future and their employees.
"The furlough scheme announced by government is meant for the whole economy, including many enterprises which might be regarded as providing entertainment or otherwise dependent on elite talent. We do agree with you that restraint needs to be shown by all and we and our clubs are doing just that. Individual clubs will need to make these decisions based on their own forecasts, as each club will have its own unique position. Government's measures have considered the whole economy."
On Monday, Liverpool abandoned plans to use UK government funds to pay the salaries of furloughed non-playing staff at Anfield after being subjected to intense criticism from former players, supporters and the media for the move, saying they are "truly sorry" for the controversy.
The Premier League leaders had announced on Saturday that they planned to follow the lead of Newcastle United and Tottenham by applying to the Coronavirus Job Retention Scheme -- a government backed financial safety net -- to pay 80% of the wages of furloughed staff. Liverpool had been due to pay the remaining 20%.
Meanwhile, Tebas has said Spanish clubs also stand to lose €1 billion if the football season does not restart, although he insists that is not a scenario which is being considered at present.
The Spanish league, along with all of Europe's major competitions, is suspended amid the coronavirus pandemic.
The stoppage is hitting clubs financially, with matchday revenue lost and uncertainty surrounding broadcasting deals and sponsorship agreements.
Barcelona are among the clubs to have reached an agreement for their players to take a wage cut during the crisis. A statement first released by Lionel Messi last week said the Barca squad would be taking a 70% reduction to their salaries.
"If we don't resume, the economic impact on Spanish clubs, including money from European competitions, would be worth around €1bn," Tebas said in a video call with international media on Tuesday.
"That figure is not just based on league revenue, but also includes money teams won't get from Champions League revenue. The losses will be €300 million if games are played behind closed doors and then €150m if we resume with fans because of the damage that has already been caused."
Tebas said the league is working hard to minimise the economic affects of coronavirus and called on players to play their part, urging them to accept pay cuts to help Spanish clubs, who are "generally in a good financial situation" but will likely have to support these losses over a number of years.
However, the La Liga chief, a staunch critic of Manchester City and Paris Saint-Germain's ownership models, argued that outside investment in the game -- from states and billionaires -- should only be used to help reduce clubs' debts, not to give them a competitive crisis when football is able to resume.
Meanwhile, talks remain ongoing with UEFA and Europe's other domestic leagues regarding how to finish the season. Tebas said a number of possibilities are being studied, although he conceded it is likely games will be played behind closed doors when football is able to restart.
"The current scenarios being discussed are to restart the Spanish league on May 28, June 6 or or even up until June 28," he said. "But we will have to see what happens in April. And it's not just about Spain, but what happens elsewhere.
"UEFA is contemplating two scenarios for European competitions. The first one involves league and European competitions being played in parallel: leagues at the weekend and European games in midweek.
"The other scenario is for two blocks. First of all, domestic competitions would be played up until July, then European matches would be played in July or August, depending on when all the leagues can finish."
Tebas said that, with or without fans, he is confident the season, suspended indefinitely, will be completed. He pointed out that those suggesting otherwise have ulterior motives.
"We won't start that debate now as it is sterile and will only generate conflicts of interest, which is what is happening in other countries," he said when asked how championships would be decided if declared null and void.
"Just by chance, the people who don't want to continue with competitions are the ones at the bottom and competing to avoid relegation.
"But cancelling the season isn't something we are talking about. We are not considering at all that we are not going to get back to playing matches."
ESPN's Barcelona reporter Sam Marsden contributed to this report