Triple world champion Niki Lauda says McLaren's Fernando Alonso should "stop complaining" and get on with the job of catching team-mate Lewis Hamilton.
Alonso has played second fiddle to team-mate Hamilton this season
Alonso has been locked in a bitter battle with his McLaren rival this season and Lauda believes the Spaniard has lost his focus.
"Alonso is using all kinds of excuses," Lauda told BBC Sport.
"Instead of complaining, moaning and bitching, Alonso needs to concentrate on driving quicker."
Alonso moved to McLaren at the end of last season after winning the world championship with Renault but has been overshadowed by rookie Hamilton.
The British star has had a superb start to his Formula One career and leads Alonso in the standings by seven points going in to Sunday's Turkish Grand Prix.
Lauda added: "My worry is if he continues to find the reasons somewhere else, and not in his right foot, he will lose out because Hamilton is doing a perfect job, simply concentrating on his driving and he's quick. It's what Alonso should do."
I brought to the team half a second, six-tenths, whatever, and I don't see anything giving me back
The rivalry between the pair has simmered all season but became public after the last race in Hungary at the start of August when they ended the weekend not on speaking terms.
Alonso had claimed pole in Hungary but was demoted five places on the grid for impeding Hamilton in qualifying, in reaction to the Briton ignoring team orders to let Alonso pass earlier on.
And Lauda believes Alonso should follow Hamilton's lead and focus on performing well.
"McLaren has the best set up with the two most competitive drivers fighting each other like crazy to go quicker," Lauda added in an interview on Radio 5live.
"When they drive, all they have to do is push the throttle. All the politics before and after does not really count.
"There is always mistrust between drivers in the same team but the drivers push eachother and they drive quick.
"My worry is that if Alonso continues to find reasons somewhere else and not on his right foot, then he will lose out.
"Hamilton is doing his bit and simply concentrating on his driving and he is quick. That's what Alonso should do."
After Alonso and Hamilton apparently, settled their differences in Turkey, the Spaniard again revealed his discomfort with the McLaren team.
"It is always very clear in any team to have equal opportunities and [an] equal car to your team-mate," he said.
"What I think sometimes and what I [have said] to the team is I gave a lot to the team when I arrived in December.
"I remember the car I drove and the results they had in 2006 and now I brought to the team half a second, six-tenths, whatever, and I don't see anything giving me back. That's the only thing."