It is ironic that the government has been so badly wrong-footed over the deportation of foreign-born offenders.

After all, three years ago it was aware that there was a potential problem in relation to asylum seekers convicted of crimes in the UK.

The response of the then Home Secretary, David Blunkett, was a promise to extend the Nationality, Immigration and Asylum Act 2002 to enable all asylum seekers sentenced for serious offences to be deported upon release.

Those given two years jail or longer were already liable for deportation under the act. It is difficult to say what impact this had on the number of subsequent deportations.

But the current Home Secretary, Charles Clarke, says that about a third of the total foreign prisoner population - that is about 3,000 people - were removed in 2004-5. And the home secretary already has wide, if infrequently used, powers under the 1971 Immigration Act to deport someone where it is deemed to be "conducive to the public good".

Existing powers are good enough if they were administered properly

So, does the government need to consider bringing in more legislation?

Barrister Simon Cox believes it doesn't.

"The law change proposal is a smoke-screen. The real issue is the failure of the Immigration and Nationality Directorate to operate the existing system effectively," he says.

But one reason why the system creaks so badly is that there are too many exemptions to the principle of deportation.

The chair of the commons home affairs committee, John Denham, argues that introducing a clear presumption in favour of deportation will, at the very least, help reduce the backlog of cases and enable IND and the prison service to begin to get on top of the problem.

That is, unless legal and political pitfalls do not derail the government's intentions.

Potential obstacles

One potential obstacle is a new European Union directive, which, depending on the interpretation, may prevent a national government from expelling an EU citizen solely on the basis of a criminal conviction.

nother is the Human Rights Act which could almost certainly be used to stop a deportation to a country where someone's life may be at risk.

It may also thwart the government's argument that any foreign-born individual convicted of an imprisonable offence, whether or not a sentence of imprisonment is actually given, should face deportation.

When the home secretary publishes a consultation paper in a few weeks setting out his proposals in more detail, they will come under intense scrutiny.

Only then will we know whether the robust rhetoric of his Commons statement has been subjected to a reality check.