A furious Dermot Desmond had a pop at a BBC journalist investigating his tax affairs, asking: "Are you a Rangers supporter?"

The Celtic tycoon wrote to BBC investigator Mark Daly a day after the journalist had approached the Irish billionaire at Parkhead asking him to justify his private jet company’s tax arrangements.

READ MORE: Celtic shareholder Dermot Desmond's private jet firm 'used offshore tax haven'

Desmond wrote: "Are you a Rangers supporter? You ambushed me last night on the way to a Celtic game in the company of my family and friends."

A private jet company formerly owned by Celtic’s biggest shareholder, Dermot Desmond, has been accused of using an “aggressive” offshore tax avoidance scheme by a leading QC.

The Irish billionaire owned Swiss-based Execujet for eight years until he sold it in 2015.

Irvine Times:

Emails from the leaked Paradise Papers reveal Execujet asked a law firm to open an Isle of Man company in 2012 which allowed Swiss taxes to be avoided.

More than 13 million documents have been leaked from the offshore law firm Appleby.

It was revealed that a number of politicians, celebrities, corporate giants and business leaders to secretive overseas arrangements.

READ MORE: Celtic shareholder Dermot Desmond's private jet firm 'used offshore tax haven'

BBC Scotland’s investigations team, which was involved in the global media leak, uncovered that Mr Desmond’s company Execujet may have avoided up to $1.3m (£1m) in Swiss taxes over three years.

The documents revealed that Appleby staff set up a company in the Isle of Man, called ExecuJet (IOM) Limited, as its primary insured office.

This led to the avoidance of a five per cent stamp duty levy on an insurance premium and tax on a “brokerage” fee from its insurers.

The offshore structure implemented by Appleby is legal but tax expert Philip Simpson QC told the BBC it appeared to be “an aggressive avoidance arrangement”.

READ MORE: Celtic shareholder Dermot Desmond's private jet firm 'used offshore tax haven'

He said that the Isle of Man company seemed to be controlled from Switzerland, which could make it liable for taxes there.

Mr Desmond strongly denies his former company had avoided tax.

He told the BBC it was “tax and regulatory compliant in all jurisdictions it operated in”.

Questioned outside Celtic Park before last week’s Bayern Munich Champions League tie, Mr Desmond said it was “absolutely wrong” to say Execujet was a tax avoidance vehicle.

Pressed further by the BBC’s reporter, he replied: “I’m not duty bound to educate you in how we run our affairs.

“Every company in the Isle of Man is not for avoidance of tax.” He declined to give further details for reasons of confidentiality, but later wrote to the BBC .

READ MORE: Celtic shareholder Dermot Desmond's private jet firm 'used offshore tax haven'

In the letter, Mr Desmond said: “There are good operational reasons for having a presence in the Isle of Man and many international companies do so. Similarly, my aircraft arrangements and my shareholding in Rietumu are fully tax and regulatory compliant. Any allegation to the contrary is a lie.”

Execujet said: "ExecuJet, a private company, operates in many countries around the world.

"It is very important to ExecuJet that it is compliant with all tax rules globally.

"Several years ago, ExecuJet chose the Isle of Man as it is a centre for insurance and re-insurance companies providing an attractive financial and fiscal environment.

"However, for some time now, ExecuJet IOM has not been required and is therefore no longer used."