Adrian Newey claims Red Bull evaluated a switch to Mercedes power for 2010 but were prevented from using the engines by rival teams.
The designer claimed Mercedes users McLaren and Brawn blocked a Red Bull-Mercedes deal.
Speaking at the Motorsport Safety Fund’s Watkins Lecture at Autosport International, Newey said the team considered the switch because of Mercedes teams’ performance advantage in 2009.
The Mercedes engine enjoyed a good advantage over the rest of the field last year. The lap time difference was significant – several tenths of a second. And when you have to find that kind of performance from the chassis, that’s quite a big ask.
But in the end Brawn and McLaren blocked us from having the Mercedes engine.
He said the team had also evaluated the new Cosworth engines but decided to stay with Renault for 2010 as the French manufacturer planned developments for its engine.
“We now have a good programme of development,” he added, and denied the discussions over which engine to use had delayed the development of the RB6.