Red Bull boss Christian Horner expects more big manufacturing names to leave Formula One unless there are rule changes.

The 36-year-old was speaking at the launch of his team's new RB6 car, which has a Renault engine believed to be underpowered compared to some of its rivals.

And Horner believes more suppliers could withdraw unless the FIA's rules on engine development are relaxed.

"The problem with the engine freeze is that you freeze in an advantage," he said in comments reported on www.autosport.com.

"I think the Renault has some good aspects and Renault, when the freeze came, took it a bit more literally than some of the other manufacturers. I think there is disparity currently within engine performance.

"On a fair and equitable basis, we rely on the governing body to ensure that you don't have large disparity between engines because the problem is that, as the chassis converge in performance, the engines will become a key performance differentiator, and the idea of freezing the engine was largely to eliminate the performance differential between the engines.

"I think the problem is if you don't allow some development, then you freeze in an advantage for one team or a disadvantage for another.

"So there has to be a balancing of that, otherwise we will end up with Mercedes-powered cars winning all the races - which I think is not good for F1.

"And other manufacturers may choose to leave F1 off of the back of that.

"The engine isn't supposed to be a key performance differentiator and therefore hopefully the ruling body will balance out somewhat the differences there at the moment."

The RB6 revealed in Jerez today showed slight changes from last year's car, with extra length to accommodate more fuel and an exaggerated 'v' on the engine cover.

"This car is a limousine," said Mark Webber. "We had only small aerodynamic changes so we didn't go crazy.

"It shows how clever Adrian Newey is that a lot of people copied our car (last year)."