A group of Birmingham Midshires savers and borrowers are endorsing the Save Our Building Societies campaign because the Halifax offer is not generous enough.
George Talkington, an account holder, is forming a group asking for "fair shares for all" composed of people who do not oppose the takeover on principle but will support SOBS as a tactic to get a better deal.
Talkington says that over half the membership composed of 375,000 savers who joined after January 1996 and 140,000 borrowers are disadvantaged by the offer.
SOBS itself has secured enough signatures to force an emergency meeting, but lacks the required funds of £5,000 to £7,000 to pay the £50 bond which must accompany each signature.
SOBS members Lib Dem MP Vincent Cable and Labour MPs Dennis Turner and Kerry Pollard are asking affected parties such as trade unions to put up the cash.