David Walsh, founder of the Museum of Old and New Art, is facing demands from the Australian Taxation Office that he repay $37 million in profits from the wildly successful gaming system he created.

MONA, lauded by many as a cultural icon, has become a tourism boon for debt-ridden Tasmania since it opened in January last year.

Mr Walsh told Fairfax this month that MONA’s position would be ‘‘precarious’’ if the dispute went to court and he lost.

He and associate Zeljko Ranogajec made their fortunes by developing a betting system that uses complex mathematical algorithms to place thousands of bets just before a horse race starts.

A Facebook campaign backing Mr Walsh and orchestrated by social scientist Ross Honeywill has drawn more than 3000 supporters and high-profile backing from personalities including blogger Marieke Hardy and former Greens leader Bob Brown.

The office recently ruled that Mr Walsh and others were running a $2.4 billion gambling business. Mr Walsh is contesting the claim and will be in court next month to fight paying the tax bill, plus interest, calculated from the years 2003 to 2006.

‘‘I think most people that do this stuff that I do would think it’s fair that once they say you’re taxable, paying tax is something that Australians should do, so I ... am prepared to pay tax from the point where they told me that I was taxable,’’ he told the ABC this week.

‘‘But it seems a little bit disingenuous to then backdate it a number of years, and then it seems likely that they had decided that they wanted to tax us maybe in 2006 or thereabouts and didn’t even tell us ... which puts me in a predicament because I have the usurious interest rates that they charge and, you know, it’s a bill that I can’t pay and it’s an unjust bill in my opinion.’’

The Facebook campaign page has been inundated with messages of support and posts condemning the tax office’s move.

‘‘MONA is the most important philanthropic contribution to Australia in decades. David Walsh should be adorned with congratulations and praise from our government, not shadow taxes!’’ wrote Christos Linou.

‘‘The ATO need their heads examining. Don’t they realise that David Walsh has brought a truly world class art museum to Tasmania? MONA is being recognised on an international level now and with that an interest in Tasmania. How short-sighted can the ATO be?’’ wrote James Speed.

But Mr Walsh has said there is only a small risk he would close MONA.

‘‘It is my intention to support MONA ongoing - that has been the work of my life,’’ he said this month.

‘‘In saying that, the retrospective tax bill is not something that I can service. It is, in fact, more than 100 per cent of the money I’ve made. But I expect a negotiated settlement. I’m not just saying that - I fully expect to get an outcome.’’