Civil liberties campaigners have been celebrating after the Government announced controversial powers to detain terror suspects without charge for 28 days would not be renewed.
Home Secretary Theresa May will let the order allowing the detention period expire, meaning that from Tuesday next week the detention limit will revert to 14 days.
But the Government was accused of a "shambolic" approach to national security policy as MPs were only informed of the plan when Home Office minister Damian Green was summoned to the Commons despatch box to answer an urgent question.
Mr Green said the Home Secretary would unveil the result of a sweeping review of counter-terrorism powers next Wednesday, but in the interim the Government would let the 28-day order lapse.
Mr Green said: "This Government is clear that the power to detain terrorist suspects for up to 28 days before they were charged or released was meant to be an exceptional power. This was always Parliament's intention. But under the last government it became the norm, with the renewal of 28 days repeatedly brought before the House. This was despite the power rarely being used. Since July 2007 no-one has been held for longer than 14 days despite the many terrorists arrested since then."
He said the Home Secretary, who was at a ministerial meeting in Budapest, would next week "set out the detailed considerations of the Government in determining whether the current regime of 28 days should be renewed and if not what should be put in its place".
Mr Green told the Commons: "The Government is clear that we need appropriate powers to deal with that threat but those powers must not interfere with the hard-won civil liberties of the British people."
Shadow home secretary Ed Balls, whose question forced the minister's announcement, said: "This is a deeply arrogant way for the Government to treat this House and it is a shambolic way to make policy on vital issues of national security."
Campaign group Liberty welcomed the move, but called on the Government to scrap control orders in next week's statement.
Liberty's director Shami Chakrabarti said: "A month's detention without knowing why is shamefully long for any democracy. The Government is to be congratulated for reducing this period. However control orders allow punishment without charge not for months, but for years on end. It would now be completely contradictory not to scrap this even greater embarrassment."