Home secretary Jacqui Smith has said intelligence services had not asked for an increase in the time terror suspects can be held without charge.
Speaking on BBC One's Andrew Marr Show, Ms Smith said MI5 had spoken of a growing threat to the country but never specifically requested legislation regarding the holding of suspects.
Asked about whether MI5 had pushed for increased detention powers, she said: "No, not directly, but nor did they ask for the extension from 14 to 28, nor did they ask for the extension from 7 to 14."
The home secretary expressed hope that the legislation would pass through parliament even though at least 30 Labour MPs as well all opposition MPs have vowed to oppose it on the grounds of safeguarding civil liberties.
She also flatly denied that the Democratic Unionist Party had been offered incentives in exchange for their support for the proposal.
Yesterday, prime minister Gordon Brown urged all Labour MPs to back the 42-day proposal which will be tabled in the house on Wednesday.
In his letter to Labour colleagues, Mr Brown wrote that civil liberty concerns were being kept in mind whilst ensuring the need for improved security.
"In the legislation currently before Parliament, we have done everything in our power to protect the civil liberties of the individual against any arbitrary treatment, because in Britain liberty is, and remains, at the centre of our constitutional settlement.
"The challenge has been to make sure that, through proper judicial and parliamentary oversight, we both keep the public free from the threat to our security, and secure the fundamental liberties of the citizen," he added.
The government has maintained that plans to hold suspects for a further 14 days are necessary due to the increasingly complexity of terrorism investigations and the scale of the threat.
In November 2005, former prime minister Tony Blair suffered his first Commons defeat over legislation to extend the period terror suspects can be held without charge to 90 days.