The cost of policing the Pope's visit to Britain could reach £1.5 million, police chiefs said today.

South Yorkshire Police Chief Constable Meredydd Hughes, who is co-ordinating the unprecedented police operation that will see the Pontiff visit London, the West Midlands and Scotland, said the figure could rise further as changes were still being made to next week's four-day visit.

More than three-quarters of Britons do not agree that the taxpayer should help foot the bill for the visit, which could reach £20 million, including up to £12 million from taxpayers, but the Archbishop of Westminster Vincent Nichols said it would be a "sad day" when the UK "closes its doors and says we can't afford state visits".

Today, Mr Hughes said: "Quite frankly we haven't estimated a total cost yet because plans change at the last minute.

"There will be changes to plans just through the hurly burly of running operations in London and Birmingham, two of our biggest cities."

No previous state visit has involved so many different sites around the country, dignitaries rarely "venture outside of London", and the Pope's visit will be both a civil and religious event, he said.

Nobody wants "a giant security operation with a religious service bolted on the back", he said.

Speaking at a briefing held by the Association of Chief Police Officers in central London, he said that while officers would look after the "safety and dignity" of the Pope, they would also protect those wishing to see him and any protesters against his visit too.

"There is no intelligence to suggest any specific group will attack the Pope," he said, adding that the last few attacks on the Pontiff were by Catholics.

Sharon Rowe, assistant chief constable of West Midlands Police, warned the beatification ceremony of Cardinal John Henry Newman at Cofton Park, Birmingham, on Sunday, September 19, bringing the revered 19th century clergyman a step closer to sainthood, will be a "ticket-only event".

The only chance others will get to see the Pope in the West Midlands will be as the Popemobile moves at a "fast walking pace" of about 4mph or 5mph along a three-mile stretch of Hagley Road in Birmingham.

Commander Bob Broadhurst, of the Metropolitan Police, who will be responsible for protecting the Pope, warned people not to underestimate the "passion and the fervour" that the visit would bring.

"People get very passionate and very, very emotional," he said. "We may at times be protecting the protesters from the faithful if one or two people get hot under the collar."

He added that the crowds were also likely to include people of all ages, from the very young to the elderly, which may create problems for the ambulance service.

Mr Broadhurst continued: "We are very used to protecting people, be they the Pope or the President of the United States.

"The big issue for me that we will have in policing terms is getting that blend right between a security operation, keeping him and his entourage safe, but giving access to the faithful and those that want to come and see the Pope and celebrate their Pope, giving them as much access as we can."

But he added that other events, including a full football programme, were continuing during the visit and the police operation would be "nowhere near the scale of the Notting Hill carnival".

The police chiefs said they were planning for "tens of thousands" of people to be on the streets trying to catch a glimpse of the leader of 1.2 billion people worldwide, 17% of the world's population.

Pope Benedict is due to begin his visit on Thursday, September 16, in Edinburgh where he will be received by the Queen before celebrating Mass at Bellahouston Park in Glasgow.

He will visit London for two days where his schedule includes a meeting with the Archbishop of Canterbury Dr Rowan Williams, an address at Westminster Hall and a prayer vigil in Hyde Park.