OurKingdom is supporting Liberal Conspiracy’s campaign against 42 days detention, and will be publishing a series of posts about it over the next few weeks. Labour rebels will decide whether the bill passes or not. For a full list of those who rebelled last time (on 90 days detention), including email addresses, click here.

Stuart Weir (Cambridge, Democratic Audit): It's funny what constitutes a ‘gaffe' in present-day politics and what doesn't. As he prepared to announce proposals for up to 42 days detention in January, the minister Tony McNulty gave an interview to the Daily Mirror warning that the country may suffer "two or three 9/11s" or "two 7/7s", saying, "Given the evidence we've got and the nature of the plots so far disrupted, such scenarios aren't fanciful."

If sheer stupidity and silliness were the measure for a "gaffe", then McNulty's comments would have ranked very high on the political richter scale. But the measure in our politics is the amount of embarrassment a statement generates for colleagues. So we can only assume that the Prime Minister and Home Secretary approved of the interview. No doubt they were also content when Jonathan Evans, Director General of M15, stated publicly that there were now 2,000 people in the UK who posed a direct terrorist threat. His intervention, delivered quite coincidentally on the eve of the Queen's Speech, which trailed the new Counter-Terrorism Bill, was widely reported as signalling that there had been a significant increase in the threat to the public.

This goes to the nub of the government's case for the extension - that the threat from terrorism has increased since the existing 28-day limit was set last year. In fact the case is nowhere near proven. The Joint Committee on Human Rights (JCHR) asked McNulty himself, in September 2007, whether the threat had increased since then, and he replied that the threat was at a very high level, but admitted that it was "pretty well the same" as it was at the same time the previous year. Senior police officers informally told the committee much the same thing in October.

But what of the MI5 Director General? What has he to say? Unfortunately, though he was prepared to give a public lecture about the level of the terrorist threat, he has refused to give public evidence to the JCHR, the parliamentary committee charged with advising Parliament and the government on the compatibility of counter terrorism measures with human rights. He refused a request to give evidence to the committee, saying that he was responsible to the non-parliamentary Intelligence and Security Committee and offering merely a private briefing.

The committee admirably turned down this offer since its members have argued constantly that there is a basic need for independent democratic scrutiny of the government's assessment of the threat from terrorism; otherwise, how can they and we make meaningful judgments about whether its measures are proportionate to the threat? It hardly helps us to have confidence in government when ministers seek to frighten us with images of three 9/11s.

The second strand of the government's case for extending pre-charge detention has a very familiar sound to it - the trend towards the increasing complexity and scale of terrorist investigations. This argument is identical in nature to those the government relied on when trying to make the case for 90 days. It now rests on the fact that in two recent investigations suspects were charged on the 28^th day - that is, at the end of the present limit. Yet it is not yet possible to examine the actual use that has been made of the 28-day period, which must await the outcome of the prosecutions of those charged.

Meanwhile, the experience of the use of the power to hold people for 28 days provides no evidence to support an extension. The Crown Prosecution Service is satisfied with the position as it now stands, as Sir Ken Macdonald, the DPP, told the Home Affairs Committee in November, adding that "our experience so far has been that we have managed and managed reasonably comfortably"; and one of his officials, Sue Hemming, in evidence to the JCHR a month later, added, "we think the 28 days has been sufficient in each case that we have had . . . We have not seen any evidence that we have needed beyond 28 days." The JCHR concluded that this and other evidence its members heard "fundamentally calls into question whether it really is ‘likely', or even that there is any ‘risk' at all, that at some point in the near future a case will arise in which 28 days is insufficient."