Lawyers for a British man wanted for a double murder in Singapore say an assurance not to hang him is worthless.
Mr McCrea ran a tax advice business in Singapore
Michael McCrea, a financial adviser from Nottingham, is wanted for the murder of his chauffeur and the driver's girlfriend in January 2002.
Australia agreed to extradite the 45-year-old in September.
He claims he acted in self-defence after the pair attacked him in his luxury flat and is appealing against the decision to extradite.
Australia, like Britain, refuses to extradite suspects to nations where they face the death penalty.
Singapore has assured the Australian Government it will not execute Mr McCrea if he is found guilty of the crime.
But his lawyer, Gerry Nash, told the Federal Court in Melbourne on Thursday: "In the constitution of Singapore specific procedure is laid down in the case of persons convicted of murder which must be followed in order for a pardon to be granted.
"The assurance is not an assurance the death penalty will
not be carried out. It is really a promise that Cabinet will in future give certain advice to the president in relation to Mr McCrea if and when he is convicted."
McCrea is appealing a decision by Justice Minister Chris
Ellison to extradite him to Singapore to face charges of murdering his chauffeur Kho Nai Guan, and the driver's girlfriend, Lan Ya Ming.
Mr Kho's body was found stuffed in a wicker basket in the
back seat of a car in a garage in Singapore's Orchard Towers complex.
The body of Miss Lan, an illegal immigrant from China, was wrapped in cloth in the car's boot.
Mr McCrea ran a business advising British and other expats how to avoid paying tax in Singapore.
His personal assistant Audrey Ong, 23, gave up her fight against extradition and was jailed for 12 years in February this year after telling a Singapore court she had helped dispose of the two bodies.
Ong said Mr McCrea killed the pair after an argument in his apartment in the Pinewood Gardens Condominium in the exclusive Balmoral Park neighbourhood.
Mr McCrea, who has an ex-wife and two children in Radcliffe-on-Trent, Nottingham, has admitted he did have a fight with Kho and Lan, but claimed he was attacked first with a knife and vase.
Mr McCrea's wife, Brunetta, and young child still live in Melbourne.
A British Foreign Office spokesman said: "Britain opposes the death penalty in all cases and we seek assurances from any country seeking extradition. I believe Australia has the same position."
He said: "Mr McCrea is subject to Australian law but when he gets to Singapore he will be entitled to assistance from the British consular officials."