One of Britain's most popular tourist attractions was shut down for three hours in an immigration crackdown.

Seven people were detained as police and immigration officers swooped at the Palace Pier in Brighton yesterday.

A police rigid inflatable vessel circled the pier in case anyone jumped overboard.

The seven arrested - five men and two women, all in their 20s - were lined up and then driven away in vans.

Among them were two Brazilians and one Colombian.

Six went to an immigration holding centre near Heathrow airport and if they are found to breaking the law they could be deported within days. One was held at the Hollingbury custody centre in Brighton.

The UK Immigration Service said it was "examining whether to prosecute" the pier owners, although the company said it had kept proper employment records.

The pier has become a favourite place to work for students from as far away as South Korea, China, Canada, Australia and the Indian sub-continent. Most earn the minimum wage.

Immigration said its operation had been intelligence-led and had been investigated thoroughly.

It was run jointly between the UK Immigration Service (UKIS), Sussex Police and representatives from other police forces seconded to the Home Office's Immigration Enforcement and Removals Directorate.

Geoff Lockwood, assistant director of UKIS, said: "This was a direct response to intelligence received that people employed on the Palace Pier were in the UK unlawfully.

"Although there is nothing to suggest that there is a particular problem with illegal working in Brighton, today's operation showed that more than ten per cent of pier staff spoken to were in breach of immigration laws.

"We will continue to act on intelligence wherever it is appropriate to do so. This operation underlines the Government's commitment to crack down on illegal working and remove immigration offenders from the UK."

The Noble Organisation, which runs the pier - the country's third most visited attraction - disputed the official version of events and said six people had been arrested, not seven.

Director David Biesterfield said the pier had been closed at the insistence of about ten immigration officers and 100 police.

He said: "A Brazilian student employed by the pier was arrested because her visa had expired a short time ago. The company had not identified the mistake due to a clerical error. The Immigration Service has acknowledged the quality and thoroughness of the company's systems and records.

"In addition, the officers arrested a further five individuals. Of these, three have at no time worked for the company, which therefore has no responsibility for them.

"The remaining two suspects are accused of relying on fraudulent documentation. Again, the company bears no responsibility.

"The company has fully co-operated with the authorities but questions whether a simple telephone call to its management, leading to the same documentary checks as have taken place, would not have been a better use of scarce police and Immigration Service resources.

"The Immigration Service suggestion that more than ten per cent of pier staff spoken to were in breach of immigration laws gives the highly misleading impression that significant numbers of pier staff are employed illegally.

"Those arrested represent less than one per cent of the pier company's current payroll."

A lawyer for Noble said: "(Mr Lockwood) has given the impression that the pier are employing high numbers of illegal immigrants and they are just not.

"If the company got anything wrong here, it got it wrong in relation to one Brazilian student whose visa had expired."

Specialist police, trained in immigration issues, came from Leicester and Kent to join a team of 20 officers for the operation.

They and immigration officials moved in just before the pier opened at 9am. The timing was deliberate to ensure most workers had turned up but members of the public would not have to leave.

All the staff were asked into the pier's Palm Court restaurant for immigration screening. Most were released and allowed to return to work. The pier opened at 12.20pm.

Graham Blackwood, immigration inspector for the Croydon enforcement unit, said a decision on whether to prosecute the pier owners would be made in the next few weeks.

He said companies employing illegal workers could be fined up to £5,000 per worker. He said proper and comprehensive employment records held by companies could be used in their defence.

The Noble Organisation said its records were faultless and it understood any document found to be forged was legally not its responsibility.

Noble stood to lose thousands of pounds in revenue from yesterday's raid and the company was concerned about protecting its reputation.

Staff and visitors were shocked by the raid.

David Jayssen, the pier's 63-year-old DJ, said: "I came down here this morning and I was a little surprised by the pier being closed up.

"But then this is Brighton and these things happen here all the time.

"A massive majority of workers on the pier are foreign."

Teresa Longley, a 46-year-old visitor from Swanley in Kent, said she supported immigration raids, especially after suicide bombings in London.

Paul Fitzgerald, a 44-year-old chemical trader from London and staying at the Hilton Metropole hotel with his family, said: "They (the authorities) couldn't have made a more public show of it."

He postponed his visit to the pier.

Anne Grainger, Noble's head of resource, speaking at the pier yesterday, said: "We collect and keep records of every single member of staff.

"We keep copies of visas and passports and work permits."