Mr Harvey told Fairfax Media that he had a caveat over Mr Tinkler's horseracing and breeding assets and was considering selling the horses that race in the name of the Tinkler company Patinack Farm.

The revelation will shock the racing and business communities as it throws into doubt the veracity of claims made last month that Mr Tinkler had done a deal to sell his bloodstock interests to a Dubai based firm, Cibola Capital. Sources close to him had suggested he'd received more than $130 million for Patinack Farm.

The timing of Mr Harvey's comments are unfortunate for Mr Tinkler. Earlier this month he claimed the money from the sale to Cibola had enabled him to finance the $150 million purchase of the Wilkie Creek coalmine in Queensland from Peabody Energy.

But on Tuesday it emerged that the proposed purchase - which surprised the Australian mining industry when it was announced in mid-May - could be in doubt, amid speculation Mr Tinkler had not satisfied contractual conditions imposed by his key backers.

Mr Tinkler had said he would pay for the mine north-west of Brisbane through his own money and financing secured from New York investment bank Jefferies. However, the sources said his failure to meet the conditions of the financing had prompted Jefferies to sound out other potential investors over the past month.

Sources said Mr Tinkler had not made as much money as expected from the sale of Patinack Farm, nor from a previous sale of an aircraft hangar in Brisbane. They said this had made it more difficult to meet the conditions imposed by Jefferies.

Mr Harvey's comments provide yet another chapter in Mr Tinkler's colourful business career, which has seen him rise from an electrician in the mines to the youngest billionaire on the BRW rich list. He built his career out of stitching together dramatic deals at the last minute from any number of left-field backers, and sources close to the now Singapore-based businessman are confident he can close the Wilkie deal. But his luck ran out last year when he was forced to sell his most value asset - a stake in listed miner Whitehaven Coal - to pay his creditors.

Although Mr Harvey would not confirm the amount owed to him, sources in the racing industry said it could be as much as $40 million.

"It has been like this for months and I have been involved with Patinack for years. I'm a big boy and I knew what I was doing when I got involved and I'm just in the middle of it now,'' Mr Harvey said. "We just have to hope [Tinkler] can get one of these deals over the line and get himself out of it."

When asked if the deal to sell Patinack Farm to Cibola had been genuine, Mr Harvey declined to comment.

The caveat means any sale of horses or property has to be approved by Mr Harvey.

In the past couple of weeks, there have been rumours that Patinack's horses could be sold off at the Magic Millions auction house on the Gold Coast, which is owned by Harvey.

Quizzed about a potential sale of Patinack's assets Mr Harvey said ''that it is not going to at present but it could change'' quickly.

''We can really have the sale at any point if we have too.''

It is unclear what assets Patinack holds, though it is believed to still own a large stud farm in the Hunter Valley and a training centre in Queensland, along with hundreds of horses. Mr Tinkler has previously sold off many of his most valuable horses - including Black Caviar's champion little brother All Too Hard - as he tried to raise funds.

Even before Mr Harvey's comments there had been suspicion about the claims that Patinack Farm had been sold to Cibola.

A man claiming to be Cibola chief Daniel Kenny told Fairfax Media, the company was buying the business ''lock, stock and barrel''.

He denied Cibola had any links to Mr Tinkler and his organisation.

Very little evidence can be found of the firm's existence apart from a website set up last year.

Mr Kenny said Cibola started life in Dubai 10 years ago. ''We operate over here as a private investment group.''

Cibola describes itself as a company ''striving to become a leader within the Arab financial sector'' but traces its roots to Sydney in 1927 as D.P. Kenny Construction. Mr Kenny refused to provide any information on Cibola's previous existence in Australia.

The company's website has been closed and a message says it will relaunch on July 1.