On top of this, Mr McGurk was costing him millions of dollars in ongoing legal disputes over the pair's soured business dealings.

The allegations are contained in a 19-page statement of facts agreed to by the Crown and former boxer Fortunato "Lucky" Gattellari, which was tendered before magistrate Allan Moore in Central Local Court in Sydney earlier today.

Gattellari, 62, once Mr Medich's friend and a collector of debts on Mr Medich's behalf, has pleaded guilty to being an accessory before the fact of murder. This carries a maximum penalty of life in jail.

Gattellari had previously been charged with soliciting the murder and being an accessory after the fact, both of which attract lesser penalties than the charge to which Gattellari has pleaded guilty.

There was no mention of whether the Attorney-General Greg Smith has granted Gattellari an immunity from prosecution but it is understood the former boxer has agreed to give evidence against Mr Medich.

The 64-year-old property tycoon is alleged to have been the mastermind behind the killing and to have provided the necessary funds to have McGurk killed.

In the statement of facts, Gattellari said that Mr Medich began demanding that Mr McGurk, 45, be murdered at the end of March 2009.

Gattellari claims Mr Medich said to him: "I need to put an end to this. I need some help from you, I need you to find someone to kill him for me."

"Are you sure about this, because there is no going back?" said Gattellari, to which Mr Medich is alleged to have replied: "Yes, I am absolutely sure, if you can find someone I want him dead."

Apart from their legal battles, which were costing Mr Medich dearly, in February 2009, Mr McGurk had illegally recorded a conversation with Mr Medich.

Mr McGurk subsequently made it widely known that he had the tape recording of Mr Medich. According to the statement, Mr McGurk was claiming the tape "would grossly implicate the government in corruption deals with Medich over the proposed development at Badgerys Creek".

The statement alleges that Mr Medich, after initially complaining about the price, agreed to pay $500,000 to hitmen organised by Gattellari. Of that amount, $300,000 was for the murder and the rest for the intimidation of Mr McGurk's wife Kimberley. The plan was to threaten Mrs McGurk after her husband was killed so that she would drop the lawsuits against Mr Medich.

At 6.25pm on September 3, 2009, Mr McGurk was shot in the head at close range as he pulled up in his Mercedes outside his Cremorne home. His nine year-old son was in the passenger seat.

Half an hour earlier, Mr Medich, Gattellari and Gattellari's friend Senad Kaminic had emerged from the Babylon massage parlour in Sydney's Haymarket. Mr Medich then headed to a bar in Bligh Street. In his statement, Gattellari said that Mr Medich wanted a "heads up" before the killing so that he could "ensure he was in a public place when it occurred".

Apart from charges against Gattellari, Mr Kaminic and Mr Medich, the two accused of the actual murder are Hassiam Safetli, 46, and his friend, Christopher Estephan, who was 19, when Mr McGurk was shot.

Both men have admitted being present when Mr McGurk was killed but both have denied being the shooter.

The court heard today that Gattellari agreed to co-operate with the police within days of his arrest in October 2010. He will be sentenced in the Supreme Court on September 7.