It is thought the "home guard" would be drawn from the existing 50,000 or so Armed Forces reservists.
Newspapers say the proposals were drawn up by senior military planners and the force could deal with all kinds of terrorist strikes including chemical, biological or nuclear attacks, which "cannot be ruled out".
A defence source told BBC News Online: "Certainly, post 11 September, we're looking with a bit more urgency at the way reserve forces will be deployed."
He said that a discussion document looking at the role of reservists was due later this week.
'Rebalancing'
Under the proposals volunteers for the force would remain with their normal units and be earmarked for availability in the event of a terrorist strike.
Receiving five or six days' extra training a year, they would be available within a few hours of an attack.
They could carry out operational tasks such as searching for survivors, securing water supplies and communications, dealing with mass casualties and organising transport.
Earlier this year the MoD said Territorial Army volunteers should play an expanded role to reduce the pressure on the regular forces.
It said that as increasing numbers of British soldiers were being deployed abroad on the "war on terror", new ideas were needed for homeland defence.
Such a force would throw into doubt suggestions under the 1998 strategic defence review that the TA could be cut in size by almost a third.
'Unpredictable'
The MoD's discussion document is thought to conclude that Britain should not follow the lead of the US in developing special military units dedicated to home defence.
Military chiefs fear such a move would hamper their ability to carry out existing roles.
The Daily Telegraph says the MoD assumes attacks on Britain would be "infrequent and unpredictable", with the possibility that several could be carried out simultaneously to maximise impact.
In February a discussion paper outlined MoD thinking on "rebalancing" the armed forces following 11 September.
Defence Secretary Geoff Hoon said he was looking at the way reservists could help meet the challenges posed following the terror attacks on the US.
He said: "One of the important questions is whether we want to use regular members of the armed forces for the purpose, particularly when they are so extensively engaged overseas."