Formula 1 teams are finding themselves in increasingly difficult circumstances, according to Michael Schumacher.
The seven-time world champion he has expressed concern about the number of teams which are struggling to pay their bills.
"It really worries me," he told Bild.de.
"Formula 1 is currently ailing financially. The world economy has become progressively more difficult to deal with. And of course, Formula 1 isn't exempt from that."
It emerged recently that the Lotus F1 team had not paid its star driver, Kimi Raikkonen, for the entirety of the 2013 season.
Meanwhile, dozens of suppliers reportedly filed claims against the Sauber team for unpaid bills earlier in the year.
It's also said that the team struggled to pay its factory's electricity bill, and that driver Nico Hulkenberg was forced to wait months for a large part of his salary to be paid.
Sauber is the subject of a rumoured merger with the back-of-the-pack Marussia team for 2014, which could see the Formula 1 grid further depleted to just 10 teams and 20 cars.
The sport has been keen to promote the fact that it has imposed cost-cutting measures including restrictions on the numbers of certain components that teams can use in a season.
Schumacher retired from the sport at the end of 2012, but is still heavily associated with the Formula 1 community, and is widely considered the best Formula 1 driver to date.