McDowell said detention centres were being seriously considered for asylum seekers from countries with a high level of application abuse. The proposal is expected to feature in the new Immigration Residence and Protection Bill, which will be published shortly. The centres would come into operation within six to 12 months of the legislation being enacted, the PD leader told a Law Society seminar in Dublin yesterday.

McDowell's remarks follow recent comments by Fine Gael leader Enda Kenny that immigrants should be refused entry if they had serious criminal records and should be deported if they were jailed here for more than five years.

Under the minister's system, asylum seekers would be held in detention centres until their applications were fully processed, after which they would either be granted permission to remain in Ireland, or would be deported.

"I don't think there's any need for barbed-wire fences, " McDowell said. "There is a very simple way of doing this.

That is to provide a centre and say, if you remain in the centre, we will deal with your application. If you leave the centre, you are deemed to have abandoned your application. We don't have to build high-security facilities to bring this about."

The justice minister predicted that his new legislation would provide much greater clarity for the immigration system. He said long-term residents would have rights close to those of Irish citizens with a sliding scale of entitlements depending on an individual's status. "Persons unlawfully here will be excluded from all but the most basic of services. I cannot accept that people should profit from illegality or that they should enjoy the same rights as those lawful immigrants who have worked hard to reach a particular level of entitlement and stake in society."

He also signalled that he is considering reform of the system for granting Irish citizenship through naturalisation, with successful applicants in the future being required to have a minimum knowledge of the Irish state as well as an ability to speak English. "We have a liberal citizenship law, but granting citizenship to someone who has little or no understanding of the Irish nation or state, and little or no capacity linguistically to participate in the day-to-day democratic life of the community is questionable, " he said.

In a pointed reference to Enda Kenny's description of the Irish as "a Celtic and Christian people" in remarks on immigration made last week, the PD leader said:

"we must stand back from assertions that the Irish nation is a Celtic and Christian people". He went on: "The truth is more complex than that, and the challenge of reconciling Orange and Green in Northern Ireland would be well-nigh insuperable if we were to lapse into a mistaken and inaccurate view of ourselves which excluded from the concept of Irishness those who fall outside a mythical descent from Celts or pre-Celts."

However, it was the minister's detention centre proposal which met with strong opposition last night.

Labour leader Pat Rabbitte said the centres would be "unacceptable", adding that he did not think that the "eve of an election is the time to pioneer such a measure".

Noeline Blackwell, of the Free Legal Advice Centre, said detaining certain categories of asylum seekers could be "a breach of fundamental human rights". She said there was "no real indication of what extra value it would bring to the asylum system, or how it would benefit Irish society, to detain asylum seekers".

Bjarte Vandvik, the Secretary General of the Brusselsbased European Council of Refugees and Exiles, said the detention systems which operated in the Netherlands and the UK were "probably the worst practices in Europe".

He said studies had shown that detention of asylum seekers had little impact on deportation policies or as a deterrent to migrants. "It simply doesn't work the way governments think it does, " Vandvik said.