Former ALP minister and powerbroker Graham Richardson says the mystery tape at the centre of a Sydney businessman's murder does not implicate Labor ministers in corruption.

Michael McGurk was gunned down in front of his son outside his home at Cremorne on Sydney's north shore last week.

Before his death he claimed he was in possession of a tape which allegedly implicates New South Wales Labor politicians in corruption.

But Mr Richardson told Channel Nine he has heard the tape and the key part which apparently exposes the Labor figures is inaudible.

He also says Mr McGurk told him it implicates bureaucrats - not politicians.

Mr Richardson says the tape contains a conversation between Mr McGurk and property developer Ron Medich - who is one of Mr Richardson's clients - and he played it to him at a meeting this year.

"The critical part, where there was supposed to be allegations of bribery was completely inaudible," he said.

"There was nothing on the tape that you could understand, neither content nor names."

Mr Richardson says Mr McGurk was allegedly trying to blackmail Mr Medich for $8 million and the matter was referred to police three months ago.

"McGurk never even alleged that there was a politician named on this tape, that's why I'm so surprised by the allegations of the last few days," he said.

"He wanted money from Ron Medich and lots of it - millions of dollars.

"About three months ago roughly I gave the police a statement about that meeting."

Mr McGurk allegedly told people his home and office were recently burgled, and he believed the motive was to get the tape - which showed that some businessmen he was dealing with were paying some ministers in the New South Wales Government.

Sydney entrepreneur Jim Byrnes last week said Mr McGurk was afraid for his life because the explosive allegations could bring down the Government.

"It's a pretty well established fact that there was supposed to be a tape recording of a lengthy conversation that he had with a person who he is currently in dispute with, and that tape recording related to supposed financial payments to very senior politicians within the state," he said.

"Had that tape seen the light of day you might be seeing a chain [effect]. You might be seeing two or three politicians no longer being politicians.

"A former NSW politician and powerbroker had reviewed the tape and as I understand it was dynamite.

"The fact of the matter was when I was told of this, my response was that it should be handed over to the Crime Commission and... copies of it should be provided to all of the major networks and newspapers.

"Not for the purpose of exploiting the politicians' naivety and stupidity, but more for the fact of his own personal protection so that the tape wasn't buried or lost."

Mr Byrnes said there could have been a long list of people who may have wanted Mr McGurk killed.