Whether they are detained during this time will depend on the usual criteria, for example if they are thought likely to abscond.

Begging asylum seekers are priority cases

Home Secretary Jack Straw said asylum seekers should not get involved in practices such as aggressive begging.

"I agree that we need to treat asylum seekers, founded and unfounded, in a decent civilised way. We need to be careful about language," Mr Straw said.

"But I also say that asylum seekers themselves do have a responsibility to recognise that they are coming to a civilised country and they have duties in terms of their own behaviour."

Immigration Minister Barbara Roche also revealed freight trains were the latest route to be exploited by organised gangs of "people smugglers".

But asylum seekers were risking death trying to enter the UK on freight trains, highlighted by the death of two Romanians who were electrocuted, she said.

Electrocuted

Last year more than 800 asylum seekers were detected in railway wagons.

At least two died en route when they tried to break out of the carriages and were electrocuted by overhead wires.

The asylum seekers mainly from Romania are smuggled aboard trains in northern Italy. Officials said 834 people were discovered in freight containers last year but it is estimated that up to 2,500 illegal immigrants used the railways as a route into the UK.