Plans to try and stop the Trident weapons system being replaced are to be discussed at the Campaign for Nuclear Disarmament's (CND) annual conference.
A White Paper is expected on the Trident issue
CND said its membership had risen since Prime Minister Tony Blair and Chancellor Gordon Brown revealed their support for a new weapons programme.
Kate Hudson, CND chairwoman, admitted there was not much time left to stop a new programme getting the go-ahead.
Mr Blair has said an independent nuclear deterrent was "essential".
Ms Hudson said: "We know that the government said in June that a decision would be taken by the end of the year on this crucial issue, so we're hard at our campaign currently and we're going to be working out this weekend how we can advance it. "
She said 59% of the public opposed a replacement for Trident and added that the conference would focus on how to force the government to have a full public and parliamentary debate.
The CND's two-day conference is being held at Bradford University this weekend.
A replacement system for Trident would need many years of development, which is why it is debated now.
At this moment the government is committed only to "retain" the weapons system, not to replace it.
Earlier this year Mr Blair said: ""It is important that Britain makes sure that we defend our country properly. I believe an independent nuclear deterrent is an essential part of that."