England fans were warned last night they will be hunted down back home if they shame the nation with racist chanting at Euro 2004.

The man in charge of the British policing operation at the tournament made the threat after he overheard fans singing racist chants in the streets of Lisbon.

David Swift was on the spot in the centre of the Portuguese capital after a group of about two dozen supporters bellowed anti-Pakistani and anti-Turkish abuse.

Mr Swift, who is advising Portuguese police, said anyone engaging in similar behaviour would be videoed by his undercover officers and attempts would be made to ban them from future tournaments.

Mr Swift said: "It is not necessarily the individuals throwing the punch or throwing the chair that are the only guilty parties.

"Using racist chanting is not acceptable at home, why should it be here?"

He did not specify particular chants, although officers will focus on anything overtly racist, offensive or aggressive.

Following the launch of a security operation at ports and airports in the UK a total of 21 people have been intercepted and barred from travelling to Portugal ahead of tomorrow's game between England and France.

Nearly 2,300 people are now subject to banning orders and another 500 are prevented from travelling to England games while their cases go through the courts.

In Portugal three English people have been arrested so far - they were all held in the Algarve for ticket touting in the street.

Mr Swift said about 23,000 people had arrived in Portugal from the UK this week although that included a large number of holidaymakers

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