The United Grand Lodge of England said about 40 members, mostly police officers and local government officials, have resigned, claiming that their careers would suffer if they were identified as Freemasons. Many others have recently left, citing "personal reasons".
John Hamill, a spokesman for the Grand Lodge, said: "This is the first time we have had a large number of resignations all giving the same reasoning. People are wondering if Freemasonry is a good thing for their careers and they are, rightly, putting their jobs and families first."
Fears among members of the centuries-old society - known to its members as "the Craft" - result from demands by Jack Straw, the Home Secretary, and Lord Irvine of Lairg, the Lord Chancellor, to create voluntary registers of Freemasons, particularly for those working in the criminal justice system.
On the recommendation of the Commons Home Affairs Select Committee, which investigated the influence of freemasonry in criminal justice matters earlier this year, the Lord Chancellor's Department has written to 5,000 judges and tribunal chairmen, asking them to disclose by next week whether they are Masons.
The move follows Mr Straw's invitation to the Grand Lodge to provide the names of judges, magistrates, police officers, prison and probation officers, and legally qualified members of the Crown Prosecution Service for inclusion in a public register of Masons.
A number of local authorities also ask staff to declare their membership of "secret societies, such as Freemasonry".
Writing in the Freemasonry newsletter, Grand Lodge News, Lord Farnham, the Pro Grand Master, urged Freemasons to declare their membership "with pride, but at the same time to register your protest at the unfairness of this discrimination".
He added: "The perception that disclosure could adversely affect an individual's employment may lead some of you to resign from the Craft in order to save your jobs."
Freemasonry is fighting to overcome widespread public suspicion over its activities. During the select committee hearing in February, members of the Grand Lodge were threatened with possible contempt of Parliament charges after refusing to disclose the names of Masons who may have been linked to three police corruption scandals.
Senior Masons are hoping to establish a legal precedent by bringing a discrimination case against an employer who unfairly sacks someone because of their masonic links. The Grand Lodge is setting up a panel of lawyers to investigate bringing such an action. Gavin Purser, the Grand Lodge's president of the Board of General Purposes, said: "Only one or two cases could be supported as legal costs will be very high."Reuse content