At the Lib Dem Spring Conference, Ming Campbell set five tests for Gordon Brown, a set of criteria by which Brown could be examined on Lib Dem values of liberty, fairness and responsibility.

As Brown moves closer to taking over from Tony Blair, he is increasingly asserting his own views and his own policies. This weekend, he announced an intention to press ahead with new anti-terrorism legislation, and in doing so issued an implicit challenge of his own: will Ming's Liberal Democrats accept a compromise on the length of detention without charge? For it is the increase in this period, above and beyond the 28 days already agreed, that forms a major part of Brown's plans:

Mr Brown wants to give police more powers - including holding suspects without charge for more than 28 days - when he takes over as prime minister.

Civil liberties campaigners warn the plan amounts to "internment".

But in a speech earlier, Mr Brown insisted he would bring in safeguards, including a judicial review of detention every seven days.

Brown is obviously trying to pitch this as a 'middle way' between the Blair/Reid authoritarianism and the libertarian objections of the Liberal Democrats and, on occasion, the Conservatives. The BBC seem to have taken this line, and have entitled their story 'Brown pledge to protect liberties', a strange title given that the first major proposal of Brown's mentioned in the story is a further erosion of liberty. Brown's 'protection' of liberty seems to consist mostly of judicial review:

He added: "We will have to consider further legislation to do so. I think that is where the public will need to recognise that we have got a new security problem."

But he said he would make sure that "at no point will our British traditions of supporting and defending civil liberties be put at risk.

"There has got to be independent judicial oversight. There has got to be proper parliamentary accountability.

"We should give the police the power to question people so we can both prevent incidents and get to the bottom of some of these very, very strange dealings."

Judicial oversight and parliamentary accountability are obviously good things. But judicial oversight is something we should have already, and parliamentary accountability is something that any responsible government should accept on all matters. These things should not be offered as sweeteners to a deal that is fundamentally unpalatable to the majority of people, indeed to a majority of MPs, who in 2005 defeated the government's last attempt at allowing detention without charge for 90 days.

Brown does offer some positive steps - the admission of phone-tap evidence in court would allow much more straightforward prosecution of terrorist suspects, removing some of the need for the grey areas of control orders and detention without charge. But the test for Ming is this: will he accept a 'consensus' on the 'need' for harsher laws in return for claiming some success in influencing Brown? After all, allowing phone-tap evidence in court is a long-standing Liberal Democrat policy and any improvement in judicial and parliamentary oversight will be welcomed by the party. Nick Clegg's comment on the matter is somewhat ambiguous:

Liberal Democrat home affairs spokesman Nick Clegg said Mr Brown "appears a little more concerned about parliamentary accountability than his predecessor".

But he added: "It now remains to be seen whether this is just a procedural fig-leaf for more authoritarian measures or part of a genuine shift in guaranteeing and not undermining our fundamental civil liberties."

Lord Carlile goes further, seeming to suggest that a need for consensus might trump possible objections:

Lord Carlile told the BBC: "I do think it is time for the political parties to get together and to try to reach a consensus with the government, so we can move forward on terrorism legislation on the basis of fitness for purpose, rather than having a hot political debate about these desperately difficult and important matters."

It is to be hoped that a compromise is not about to be struck. For many Liberal Democrats, this is a test of principle. If Ming gives any support, even in the context of a supposedly more liberal-friendly approach from Gordon Brown, to the idea of extending the detention period beyond 28 days, he will have failed a key test in the eyes of his own supporters and party members. Britain needed the Liberal Democrats to stand firm against Tony Blair's plans in 2005, and Britain needs the Liberal Democrats to stand just as firm against Gordon Brown's attempt to revive those plans.