Gordon Brown's first foray into prime ministerial policy-making territory is also likely to provoke the first major clash with members of his own party. His proposals for reform of security measures, floated while electioneering in Glasgow, appear to be designed to underpin his aspirational credentials as the Hard Man in No 10, tough on crime and tough on terrorism. In this, he treads a dangerous path between being seen to be decisive in tackling the radicalised enemy within and eroding civil rights by introducing new laws little short of those enforced in some of the world's most totalitarian states.

The most controversial - and the one he will have most trouble driving through Parliament - is an extension of the time suspects can be held without charge from 28 to 90 days. It is a change the police would welcome to allow investigators leeway to gather evidence on individuals from various international intelligence sources. But it comes coupled to legislation which would drive a coach and horses through habeas corpus by also allowing police or intelligence officers to continue to question those in custody after they had been charged, but before they appeared in court. Critics are already muttering darkly about the creation of "mini Guantanamos" in the handful of custom-built high-security cell blocks at police stations around the UK.

Mr Brown will also face opposition from MI5 and MI6 on his plans to allow phone-tapping evidence to be used in trials. The intelligence community has always opposed this, despite its proven success in smashing Mafia-style organised crime in the United States. The stumbling block for the British spy masters is that the capabilities of GCHQ, the government's "big ear" to the electronic spectrum, and those of the ultra-secret listening post run by the US National Security Agency from a nominal RAF base at Menwith Hill in Yorkshire might be compromised. At the very least, a thinking enemy would gain valuable data from which to develop countermeasures. GCHQ also has a practical objection. The "product" it sieves from the stratosphere, commercial telephone hub links, digital highways and satellites is often raw and even more often highly sensitive. To package it for public consumption in a courtroom would be both time-consuming and labour-intensive. Officials say it would detract from the prime function of intelligence-gathering.

The Prime Minister-in-waiting says he will stump up an extra £2bn a year to fund heightened security. He does not, however, disclose the source of that windfall for the intelligence organisations. Defence chiefs, already strapped for cash and fighting two simultaneous wars on a wing and a prayer, fear some of their key projects or even operational capabilities might be raided for the money.

The new measures are also linked to suggestions that the police should have automatic stop-and-question powers. Again, this type of creeping state control will inevitably be seen as an erosion of basic freedoms. If and when ID cards are introduced, how long will it be before people are asked for their papers in the street in true Stasi style while being interrogated about their lawful movements? More to the point, those most likely to be stopped and questioned will inevitably be young, Asian and Muslim. It will probably not even be consciously deliberate on the part of the police officers. But they will justify their actions on the grounds that, while all Muslims are certainly not terrorists, current terrorists are predominantly from extreme Muslims factions. It is a recipe for further alienation of ethnic minorities and potentially a spur to the recruitment of the type of disenchanted young men who carried out the July 7 attacks in London.

Such laws were never considered necessary when the IRA was bombing London and even striking the commercial heart of Manchester and the pubs of Birmingham and Guildford. MPs should reflect in advance that it is far easier to enact new laws than to remove them once they reach the statute books and become enshrined.