Mark Webber has warned he will quit formula one if he cannot find a top seat for 2013.

The 35-year-old Australian is the only prominent member of the leading Red Bull team who does not currently have a contract beyond this season.

It is rumoured Dr Helmut Marko wants to replace him for 2013 with either Daniel Ricciardo or Jean-Eric Vergne, triggering rumours Webber could be a potential replacement for Felipe Massa at Ferrari.

"The only possibility is if Massa decides to leave Ferrari, or Ferrari decides to leave Massa. There could maybe be an opening there," 1980 world champion Alan Jones told GMM.

But if Red Bull and Ferrari both pass up Webber, his options for 2013 appear limited.

"I'd need something competitive," Webber told the Australian news agency AAP on Tuesday.

He warned that he would not consider sliding down the grid to a less competitive team.

"It's pretty clear that I've earned my stripes on the way through so I won't be doing that on the other side -- going the other way," said Webber.

"Being competitive, being at the front, is certainly a big, big factor of me staying very hungry and motivated."

And so hungry is the 2011 Brazilian grand prix winner that, according to F1's official website, the already-lean and tall Webber has lost weight ahead of this season.

"I am no light version -- I've just lost some kilos, that's all," he confirmed.