The improved deal is reward for McDonald's 31-goal debut season following his £700,000 move from Motherwell.

The Australian had two years left on his previous contract, with the option of a one-year extension, but his spectacular goalscoring form prompted Celtic to secure his future until 2013.

And the 24-year-old knows that being a mainstay of the Celtic team over a decade would be an achievement in itself.

When asked if he wanted to stay at Celtic for the rest of his career, he responded: "I have always said that, and if that is the case you know you have had a successful career because you don't play at a football club like this if you are not doing it week-in, week-out.

"So if I could do that, I think I would have certainly had a very good career."

Newcastle were reported to be preparing a £6million bid for McDonald in the spring but the striker's agent began talks over the new deal as soon as Celtic clinched their third successive title.

And, after signing the contract following his three-week tour of duty with the Australian national team, McDonald admits he would think twice about leaving Celtic for England.

McDonald, who was released by Celtic manager Gordon Strachan while a teenager at Southampton, said: "The money down in the Premier League is astronomical and I think that's the main reason a lot of these teams are being linked with players from Scotland.

"Money is always going to be a big issue in football, but this club has a massive history and you only need to come and watch Celtic in front of 60,000 to know how special a place this is.

"A lot of people have left and probably regretted it. So it's certainly one thing that would go through my mind if it was ever to come about.

"But I'm just thankful that now I have secured my long-term future and I'm here to annoy everyone for another five years.

"For the club to show that kind of belief in me boosts your confidence right up there.

"Not that I wasn't confident beforehand, but it's a great feeling and makes you feel wanted. I'm looking forward to more successful times at Celtic."

While the confident McDonald exceeded the expectations of probably everyone but himself last season, he knows he could be accused of being a one-season wonder if he has a slow start to the coming campaign.

And while he refused to boast that he can better his scoring record, he is still focused on improving as a player.

"There is always something to prove, no matter how well you have done," said McDonald, who was rejected by Dundee United before his successful trial with Terry Butcher's Motherwell.

"It's all good having a good season last year but I believe this could be the making of me this season if I was to go out there and do it again.

"It shows people that it is not just a one-off season where everything he hit just went in, he is up there as a good striker.

"I'm not going to put extra pressure on myself and tell you I'm going to score 35 next year.

"I have personal targets but all I can do is work hard week-in, week-out and I've got to do that to keep in the team anyway.

"There is no guarantee of starting every game, you don't get a free ride at Celtic, that's for sure.

"You have got to work hard for every inch, and hopefully I will be as successful as last season.

"My goal will be to improve on that. If you ask any footballer they will tell you they want to improve on the year before and become a better player, and I'm no different.

"Hopefully I can score a few more goals but we will just have to wait and see."