Pupils will no longer be required to study citizenship at secondary school when England's national curriculum is slimmed down, it is claimed.
The Association for Citizenship Teaching says it understands the subject will be made non-statutory in the coming curriculum shake-up.
It fears this will mean the end for a subject which, it says, chimes with the Tories' Big Society idea.
The government said it had not decided the future status of any subject.
It is due to set up a panel of experts later in the autumn to review the curriculum and has pledged to give schools more freedom over what they teach.
But Education Secretary Michael Gove has made no secret of his desire for a much-reduced national curriculum and his preference for a return to more traditional subjects such as history.
It is thought that removing the requirement for secondary schools to teach citizenship might allow for that.
Jamie Kelsey Fry, a board member of the Association for Citizenship Teaching, said the subject was all about creating an informed, enabled and politically engaged generation of young people.
Encouraging people to become active citizens in the so-called Big Society was one of the Conservatives' key themes, he said, and citizenship teaching was the ideal subject to aid this.
The subject has won the support of singer Jarvis Cocker, who said it encouraged children to use the knowledge they picked up at school rather than just "passively accumulating it in the hope of passing some exams".
He added: "If you truly want a Big Society then surely giving people the tools they need to engage with society is essential."
'Issues that matter'
In the citizenship classes, young people learn about democracy and justice, the structure of political systems and how to function in that structure.
Mr Kelsey Fry added: "They learn to use their own critical thinking skills and to understand the issues that mean the most to them and then they learn to take action upon these issues themselves through authentic projects.
"This isn't simply encouraging young people to go out and protest - it is more about getting them working within the traditional political process so they can address the issues that they care about.
"They do projects where they are writing to MPs and working with local councillors. They do research about the issues that matter to them."
He added that it was a very good way to engage young people with their education.
"There are many students who are not strong academically in other subjects but they can really flourish in citizenship," he added.
National Union of Teachers head Christine Blower said it would be a very regressive step to make citizenship non-statutory.
She said citizenship was about getting young poeple engaged in society and was good for very academic pupils and for those who were not so academic.
Green Party MP Caroline Lucas said: "The coalition talks about a "Big Society" of active citizens. But true democracy relies on people being politically literate, being able to evaluate key issues, and then to take informed and responsible action to make their voices heard."