Archbishop Vincent Nichols, the leader of Catholics in England and Wales, said Pope Benedict's visit in September would offer iconic moments including "standing side-by-side" with Queen Elizabeth, supreme governor of the Church of England.
But the cost is set to rise to 10-12 million pounds, up from an initial estimate of about 8 million pounds, the Prime Minister's special representative for the Papal visit, Chris Patten, told reporters.
The Roman Catholic Church's contribution is also expected to rise from its original estimate of about 7 million pounds. It has raised about 5 million pounds so far, largely from its 5 million worshippers and private donors.
Security costs, including policing, have yet to be revealed.
The former Conservative minister and governor of Hong Kong said the initial cost had underestimated the "complexity and sophistication" of the visit which combined state and pastoral elements.
On Sunday, the coalition government asked many departments to plan for possible cuts of up to 40 percent, far more than announced in an emergency budget last month.
It said severe cuts and tax hikes are needed to tackle a record peacetime budget deficit of about 11 percent of GDP to restore market confidence and avoid the fate of debt-ridden countries like Greece.
CAMPAIGNERS' PROTESTS
The Taxpayers' Alliance, which calls for a low tax society, said "no visitor should cost UK taxpayers such a huge sum of money."
The National Secular Society, which plans to demonstrate against the visit, said the increase was "disgraceful," saying it would intensify its campaign.
"An important thing is that we have not been told how much the security cost will be," Terry Sanderson, its president, told Reuters, suggesting it could cost tens of millions.
Patten said the current financial crisis should not mean that state visits should become "distant memories."
Details of the pope's four-day trip were confirmed, including an open-air Mass at Bellahouston Park in Glasgow, Scotland, and the beatification of Cardinal John Henry Newman at Cofton Park in Birmingham.
Nichols said the pope was "profoundly" looking forward to the trip between September 16 and 19.
"(He is) enthusiastic but also ... very aware of the momentum and the magnitude of this visit," he added.
The trip would focus on inter-faith dialogue, globalisation, education and the environment. Nichols said the worldwide child abuse scandal in the Church had been rightly condemned but denied it would overshadow the visit.
"I do not think we will spend the time firefighting because the overall picture of the Catholic faith and the Catholic faith in practice balances out those things," Nichols added.
SIC: ReutersUK