In addition to the immediate economic benefit from tourism and commerce, WYD will showcase Sydney and Australia in a way which it is projected will contribute to tourism and industry for decades to come, according to a briefing paper sent to clergy last week.

"Almost all our leaders – of whatever religious and political affiliation – also recognise that beyond the hugely positive economic impact, there is great social value in offering young people spiritual values and ideals, hope and reason to celebrate,” the report said.

The report says the Federal Government has committed $35 million to WYD08 and some services in kind, including visa processing for pilgrims.

"The NSW Government is not contributing cash but will provide vitally important services to help deliver the event including the provision of venues (including Randwick Racecourse), public transport for pilgrims, policing, sleeping accommodation at public schools and emergency healthcare,” it said.

WYD08 will be the biggest event in Australia's history in terms of participants. It will draw at least 125,000 people to Australia. No event of this size can be staged without the support and co-operation of the Federal and State Governments.

The Church in Australia did not bid for World Youth Day until it had clear commitments of support from both governments. The report said the Olympics, the Commonwealth Games and APEC all cost substantial public money. The 2006 Commonwealth Games in Melbourne cost taxpayers almost $900 million.

"The support required for WYD08 is nowhere near the $900 million provided for the Commonwealth Games – but it is sufficient for what we need,” the report said.

The total costs of WYD08 will depend on many factors with the most significant being the number of pilgrims who register to participate. Current projections indicate a total cost of approximately $150 million – excluding in-kind services provided by the governments and the Church.

"We expect around 70 per cent of this cost will be funded from pilgrims registration fees, the archdiocese of Sydney and other donors,” the report said.