Members of Parliament Problem

I read awhile ago that certain members of Parliament do not speak their mind regarding the situation in Northern Ireland. The reason they give is that they have children and they fear the IRA. There are times when one wishes to speak anonymously, yet speak as a member of a group. Is there a way to take published public keys and combine them with your own in such a way that your identity is not compromised, but it is clear beyond a doubt that you control one of a set of public keys? Peter Hendrickson ph@netcom.com