Ministers wanted the period to be extended to 90 days
MPs have approved the extension of a 28-day limit on holding terror suspects without charge for another year.
They have also agreed to add two new organisations to the list of banned terror groups.
Earlier the Tories said they would not seek to reduce the limit, but it should be seen as an "exceptional power".
They warned against attempts to increase the limit to 90 days - a move on which the government was defeated in 2005 - without "clear evidence".
The new banned groups are Jammat-ul Mujahideen Bangladesh and Tehrik Nefaz-e Shari'at Muhammadi.
However the group mentioned by Conservative leader David Cameron at Prime Minister's Questions last week, Hizb ut-Tahrir has not been added to the list.
The 28-day limit had been a compromise - the government wanted 90 days, but attempts to push it through ended with Tony Blair's first Commons defeat as PM.
The Terrorism Act 2006 extended the 14-day limit to 28 days, but with a clause that the changes would lapse after 12 months - on 25 July 2007 - unless a further order was made. MPs approved the extension for another year, without a vote.
Shadow attorney general Dominic Grieve said while the Tories would not oppose the order, it should be remembered Britain had "moved radically away" from the time when 48 hours was considered sufficient to hold someone before charge.
He also said his understanding was Australia's upper limit on holding suspects without charge was 14 days, while in the US it was 10 days.
He said he would like to see a return to the 14-day limit in the UK eventually "if at all possible".
He raised concerns that holding people for long periods before they were charged was fuelling media speculation and was risking prejudicing future trials.
The Liberal Democrats' home affairs spokesman Nick Clegg said his party's support for the measure should not be taken as a signal they would back a further lengthening of the detention period.
Tory MP John Bercow suggested the number of individuals held for the full 28 days "could be counted on the fingers of one hand".
Home Office Minister Tony McNulty said six people had been held for the full 28 days - three of whom were charged and three who were not.
He said the government wanted "substantial debate" on terror laws adding: "We are very, very serious about that consultation."
But he said the government believed "at the very least" the case had been made for 28 days' detention - but said they had to take a collective view about whether "in utter extremis" suspects should be held for longer if required.
"The police, along with the security services, the government and all right-thinking people want to bring these people to court in the swiftest fashion at the earliest opportunity," he said.