ABU DHABI (AFP) - Red Bull were excluded from qualifying and relegated to the back of the grid for the Abu Dhabi Grand Prix for using illegal cars, race stewards said on Saturday.

A technical investigation of their cars - driven by four-time champion Sebastian Vettel and Daniel Ricciardo - resulted in claims that they were fitted with illegal parts.

In a ruling statement on the issue, stewards told the team that they had "determined a breach of the regulations had been committed".

In an earlier brief statement, Jo Bauer, the Formula One technical delegate of the sport's ruling body, the International Motoring Federation (FIA), said the front wing flaps of both Red Bull cars were too flexible.

Red Bull said they had been unfairly treated by the stewards.

"We are disappointed that we have been singled out for a front wing deflection test when it is clear that other teams are interpreting the rules in a similar fashion," said the team in a statement.

"The team accepts the decision of the stewards and will start the race from the back of the grid."

Sunday's 55-lap race will be Vettel's 113th and final one with the Red Bull team after winning four world titles.