Tests revealed the problem following Saturdays 23-16 defeat to England, and the versatile three-quarter has now been ruled out of Australias clash with Ireland this weekend.

It is not known if Giteau suffered the fracture after coming on as a replacement against England or whether he has aggravated an existing injury.

Meanwhile, Australias reserve prop Nic Henderson has been called up as front-row cover after Matt Dunning injured his neck during the Twickenham defeat.

Dunning was taken from the field on a stretcher after he injured his neck during a scrum collapse 10 minutes before the end of the match.

He underwent X-rays at the ground, but was taken to a London hospital for further scans after complaining of general pain in his neck.

I just felt a bit of strain in my neck and the medical staff wanted to make sure we did everything right and be cautious, Dunning said.

The scans have revealed it's just a joint strain which is good news.

Henderson, who has two Wallaby caps, was a member of the Australia A side which opened the tour with a 42-12 win over the French Barbarians in Bordeaux earlier this month.

The Wallabies will play against Ireland at Lansdowne Road on Saturday, before completing their European tour with a Test against Wales in Cardiff the following weekend.