"The time is now right" to reconsider extending detention without charge beyond the current 28 days limit, Home Secretary Jacqui Smith has said.
Terror suspects have been charged before 28 days elapsed
She said the complexity of recent alleged terror plots meant more time was sometimes needed before charge.
Ms Smith, appointed in June, said the 28-day limit had already "been pushed".
She was appearing before the home affairs select committee a day before the Home Office publishes a document on tackling terrorism.
Ms Smith succeeded John Reid as home secretary, and was immediately faced with attempted car bombings in London and an attack at Glasgow Airport.
She told MPs on Tuesday: "There is certainly information that recent alleged plots are more complex, contain more products - whether or not they are phones or computers or witness statements or house searches - than was the case when Parliament considered this previously.
"And what we know about international connections and the experience of investigating up to this point all give us at least a strong view that the time is now right to reconsider whether or not, and how, it might be necessary to allow longer than 28 days for pre-charge questioning."
She said the Home Office would be outlining its "analysis" of the increasing complexity of plots, the nature of plots such as the likelihood of suicide bombings, the international aspects, and the way in which the extension from 14 to 28 days has been used.
But she did say the document would "not plump down on one particular solution".
"If there was an extension it will go alongside both Parliamentary scrutiny and judicial oversight," as well as considering other options, she said.
Questioned about how the limit had been used so far, she said it "has been pushed".
"In recent operations...one person was held for between 14 and 15 days then charged, four held for between 19-20 days and then charged, and six people were held for 27-28 days and three of those were charged.
"There is already evidence of us going up to the point of 28 days," she told MPs.
The government had originally wanted police to be able to hold terror suspects for 90 days without charge - a call which led to Tony Blair's first Commons defeat as PM.
A compromise eventually saw the previous 14-day limit extended to 28 days, but a number of ministers have said they still favour a longer detention period.