Scott McDonald last night admitted he lifted his shirt after scoring in Celtic's recent win over Hamilton Academical to prove he was not piling on the pounds.

The Australian striker, who is currently in his homeland on international duty, conceded that he is still short of full fitness, but insisted there was good reason for that and that he will prove his critics wrong.

The 25-year-old said: "I didn't take too kindly to suggestions that I was overweight. It's just a load of nonsense, but it's something that inspires you to go out there and chuck it back at them.

"My fitness hasn't been up to scratch, but people have got to realise that when you've been out for three to four weeks with a groin injury and you've only played two games at the start of the season before that, you haven't had much game-time.

"I can assure you everything is fine, my weight is the same as it was last season when I was scoring goals and I'll continue to work hard to get fitter.

"Hopefully that will see me get back to the top of my game and have me scoring goals for my club and country."

McDonald is hoping to feature in Australia's World Cup qualifier against Qatar in Brisbane tomorrow, before facing the long journey back to Scotland ahead of Celtic's trip to Inverness for Saturday's lunchtime kick-off.

He said: "It would be nice to finally get my first goal for my country. It's been a while in the waiting and I don't want to wait too much longer."

Meanwhile, Artur Boruc, his Celtic team-mate, insists he learned a valuable lesson after being left out of the Poland squad last month.

The goalkeeper was dropped from Leo Beenhakker's plans after his alcohol-fuelled antics after a friendly in Ukraine in August, but returned to help Poland to a 2-1 win over the Czech Republic last Saturday with a string of fine saves.

Boruc said: "The last few weeks have been a very dark chapter in my book, but I believe all that is now behind me and that I can learn from it, move on, stronger than ever.

"I have tried to stay calm because I knew I could come through this mess. Of course, I regret what happened, but, sometimes, you need to experience such things to grow as a person and as a pro.

"I can't complain with the coach's decision to kick me out of the team. The players must respect him and, I suppose, he was saying guys, I'm the boss here'. I accept that and I agree with him."

He added: "Against the Czechs, I was lucky. Somehow their shots were directed exactly where I was standing.

"It was a great result for us and it leaves us in a very good position in the group."

Boruc has complained of a groin problem, but should be fit to face Slovakia tomorrow.