At present, there are 200 places in the centres. More than 120 people have been detained for more than a month, according to the latest Home Office statistics. Twelve have been detained for more than six months, and one for more than a year.
Asylum seekers are detained at their port of entry if immigration officers think they are likely to remain in Britain and go into hiding. However, Charter 87, which campaigns for refugees, said yesterday that officers would be told to clamp down on applicants, detaining 'virtually all of them'.
'If they are providing this number of places, they are going to use them,' Louise Pirouet, co-ordinator of Charter 87, said.
Under Home Office proposals, applicants would have just two days to appeal against a decision to refuse them asylum. But if they were in detention centres it would be difficult to get advice from lawyers specialising in asylum work within that timescale, she said.
'In our opinion, these plans are likely to mean that many people who urgently need protection may well be sent back to persecution.'
The claims were denied by the Home Office which said the increase in detention centres mirrored the rise of illegal immigration. However, a spokesperson conceded that applications for asylum from people arriving in Britain had declined substantially.