Mark Webber admits Red Bull have been forced on 'to the back foot' after a double retirement in Sunday's Italian Grand Prix proved they are now involved in a scrap to defend their drivers' and constructors' world titles.

The 34-year-old Australian, who was forced to retire two laps from the end of a race dominated by Lewis Hamilton for McLaren, said the team had 'a few technical issues'.

German team-mate and defending champion Sebastian Vettel was also forced to abandon the race after being hit earlier with a drive-through penalty for forcing Fernando Alonso's Ferrari off the circuit.

Alonso recovered to finish third behind Hamilton and magnificent Mexican Sergio Perez of Sauber, but blamed Vettel for the incident and the damage it did to his car.

"At the end of the race, I had no rear tyres left," said Webber, who endured a wild slide.

"I was obviously pushing hard and, for the sake of a couple of points, I could have not pushed as hard.

"The rear tyres were completely finished though.

"And it was a poor day for us as a team. I'm not sure the last time it happened. We've had a few technical issues -- and we put ourselves on the back foot today."

The double retirement was Red Bull's first in 2012 and left them struggling to hang on to their crowns.

In the drivers' championship, Vettel has slipped back to fourth on 140 points with Webber fifth on 132 behind Alonso on 179 while in the constructors' title race their lead is now only 29 points ahead of in-form McLaren who have won the last three races.

Red Bull have 272 and McLaren 243, with Ferrari third on 226.

Since winning the British Grand Prix, Webber has finished eighth, eighth, sixth and retired as his title bid has evaporated.

Vettel has not won since the Bahrain Grand Prix in April, but has continued to collect podium finishes to keep his challenge alive.