Janiak says Takeover Target has been steroid free since 2006 (Getty)

Australian trainer Joe Janiak has responded to claims that Takeover Target should not have been invited to run at Royal Ascot.

British trainer Mark Johnston said the nine-year-old could have an unfair advantage after testing positive for a banned steroid in 2006.

Janiak said the criticism is unfair: "There's no justification for it, we were innocent at the time."

"At no stage did steroids give my horse an advantage."

He added: "It's done and we've paid the penalty."

Takeover Target was found to have the anabolic steroid 17-alpha-hydroxyprogesterone hexanoate, known as HPC, in his system on arrival in Hong Kong in October 2006.

The drug, which has the potential to build muscle, was not on the banned list of substances in Australia at the time but was outlawed in February 2008.

Janiak says HPC was recommended by vets as an aid for horses who travel abroad.

But Johnston believes the effects of drug could still be helping Takeover Target despite Janiak saying the horse has been steroid-free since 2006.

Johnston told the Racing Post: "If an athlete was taking steroids up until four months before the Olympic Games there would be an impact on performance.

"It seems that the rules for British trainers are different from those for Australian trainers with runners in Britain."

Takeover Target will be based in Newmarket for his assault on the King's Stand Stakes and Golden Jubilee Stakes at Royal Ascot, followed by a possible tilt at the July Cup at headquarters on 11 July.