Mr Blunkett's critics would be more persuasive if they recognised the things he gets right

Liberals must be prepared to admit we have a duty to consider the price of rejecting any diminution of ancient rights

In the spectrum of Labour politics, David Blunkett is nowadays a distinctly uncuddly figure. The policing announcement he made with Tony Blair yesterday, the first in a series that ministers now fervently hope will drive politics, post-Hutton, back to domestic policy, was one of his less controversial forays into national debate.

The Home Secretary looms large in the demonology of pressure groups, especially those preoccupied with human rights. Scourge of defence briefs, flint-hearted slasher of benefits for asylum-seekers, denouncer of uppity judges, and menacing would-be limiter of jury trial, Blunkett scores few credit points among those who with good reason see the liberty of the subject as belonging at the core of a government of the left.

This is why when he sounds anything like open-minded about immigration it is bound to make headlines. His firm declaration that - as of now - Britain is not following the lead of several other Western European countries and seeking to restrict the entry of immigrants from the new EU countries who want to work was a statement well worth the attention it got.

A statement of intent is not itself a policy, of course. It is still open to the British Government to reverse its decision by using the EU Accession Treaty to impose restrictions on numbers of East Europeans able to work if unemployment rises to the levels that some of his other West European counterparts have to worry about and he - for the moment - doesn't.

Blunkett argues with some persuasiveness that his much-criticised toughness on so-called bogus asylum-seekers makes space for a more welcoming approach to bona fide economic migration; that it makes the public readier to see the benefits than it would otherwise be. But that won't itself put a stop to criticisms, some of them well justified, of the way asylum claims are dealt with. On the same day as his remarks Amnesty produced an alarming analysis showing that officials are getting the decisions in initial hearings wrong in about 14,000 cases a year.

But this is a subject on which language matters. Labour has too often tried too outflank right-wing pressure by sounding just as draconian. By clearly welcoming the arrival not only of highly skilled workers but also those doing less skilled but vital jobs in sectors such as construction, seasonal agriculture and hotels and catering, he is leading an argument as politicians should.

It's a point that has been made within government for some time by the Treasury under Gordon Brown - and not just because most of these potential migrants happen to pay their taxes. And by shifting the balance of argument in favour of not restricting numbers as others in western Europe have done, Blunkett may be on a road to preventing even more immigrant labour being driven underground. If nothing else, the hideous Morecambe tragedy should remind us what happens if you leave labour shortages to be filled by the gangmasters.

There's a case for Blunkett's vociferous critics, particularly among the pressure groups that do so much that is essential to highlight injustices visited on refugees, to say as much. It doesn't detract from - and perhaps it even enhances - the authority of their criticisms if just occasionally they are prepared to congratulate him for getting something right.

But this in turn raises a larger point about the temper of political debate. Once again, Blunkett and his critics provide an illustration. Last week Blunkett characteristically enraged his critics by using a trip to India to foreshadow a drastic overhaul of Labour's already deeply controversial counter-terrorist legislation; in particular, he floated the idea that British citizens might be subjected to draconian detention powers not unlike those that have consigned 14 non-Britons suspected of terrorist activities to Belmarsh prison under the Anti-Terrorism, Crime and Security Act, six of them for more than two years. This option, which will be canvassed by Blunkett in a consultative paper at the end of the month, would be a very serious step. It follows criticisms of Part Four of that Act by eminent members of the Privy Council under Lord Newton of Braintree.

It would mean that court proceedings would be in secret, with security-vetted lawyers, because of the intelligence basis of the case. It could, if enacted, read across to the British detainees in Guantanamo, if, despite some renewed evidence of US resistance to letting them return to Britain, they are eventually allowed back. And it could provide the means for incarcerating some Britons already here, and against whom at present no possibility of a trial exists.

It was persuasively challenged by the Tory home affairs spokesman David Davis, compounding the agony of liberals who feel things have come to a pretty pass when the defence of civil liberties is left to a pro-hanging right-wing Tory. And it was immediately slammed by a range of critics from Amnesty to lawyers with a commendable interest in civil liberties.

There are no doubt very strong arguments against such a course. Although significantly less draconian than - say - the US Patriot Act or the Guantanamo detentions, because of the importance the courts still play in approving the detentions, such a regime carries at least some of the same risks; namely that the defence of Western values and the rule of law against terrorism is made all the weaker if those values are not scrupulously adhered to in Western countries.

Heretical as it is to say so on the left, however, the argument isn't as simple as the chorus of criticism implied. In the current global climate, a Home Secretary does have a duty to weigh security of the majority against a small minority who the courts are persuadable by secret evidence may be very dangerous indeed. Maybe 24/7 surveillance, however costly in terms of manpower, is a better way of containing such a threat. Maybe electronic tagging, as Lord Newton's committee proposed, can do the job; maybe even the grave risks that many in a position to know believe would survive such a strategy are worth paying as the price for maintaining blind and equal justice.

It's a truism to say that no such step should be embarked on without the fullest debate. But at the same time we liberals do a disservice to our own arguments if we are not prepared to admit that the dilemma exists; that we, too, have a duty to consider the price as well as the benefits of rejecting any diminution of the ancient rights of the defendant in all cases.

I think the balance of the argument still runs in favour of just such a rejection. But I am not quite sure. Blunkett, a more complicated politician than the two-dimensional demonology allows, has invited just such a debate. His critics do their own cause a disservice if they not prepared to answer his invitation in rational ways that acknowledge the dangers of both courses - and not just of one.

d.macintyre@independent.co.uk