Peter Siddle has insisted that England's current problems off the field is none of Australia's business.

Spinner Graeme Swann announced his immediate retirement from cricket on Sunday with England 3-0 down in The Ashes, which has led to criticism in some quarters due to the fact that there are two remaining Test matches to play Down Under.

"All I can speak for is us," Siddle told reporters. "It's every boy's dream in Australia, all I ever wanted to do was get the Baggy Green.

"To achieve that is everything I could have hoped for. There's nothing else I want to do. It's something we cherish a lot.

"I guess it was time for Swanny. He felt his time was up, [but] he's had a great career. I've enjoyed my time playing against him. He's always been a big challenge."

The fourth Test gets underway at the MCG in Melbourne on Boxing Day.