The Metropolitan Police are seeking the source of the Wild West-style posters, which claim the fatwa has been issued 'for the abduction, kidnapping and false imprisonment' of various radical clerics.
Death threat: One of the posters issuing a fatwa against Theresa May
A link on the posters directs people to a website which states: 'The current reality of Muslims living in Britain has unfortunately become very bleak; what was initially perceived by some, to be a malicious smear campaign against the Muslim community has now turned into something far more sinister.
'We understand the seriousness of this religious verdict, and will be releasing further information in due course.'
The website specifies high-profile Muslims such as Khalid al Fawwaz, 48, a Saudi Arabian with links to Osama Bin Laden who is currently fighting extradition to the U.S. on allegations of terrorism.
'A fatwa is an answer to a question, and it could relate to a political question or even a marital problem.
'But we have Muslims such as Khalid al Fawwaz who have been held in prison for 12 years without charge or evidence against them.
'What we want to do is ask Muslims if a situation like this is allowed in Islam? Should we vote for someone like Theresa May and what relationship should we have with a government like this.
'Secret evidence is used against them in these situations and there seems to be one rule for Muslims and another rule for others.
'We are not really an organisation as such, more of a community group that has come together to raise questions about these issues because something needs to be done about it.'
The posters have been spotted on phone boxes, bus shelters and walls in Balham and Tooting and are being treated 'as graffiti' by Wandsworth Council, which is treating them with a no tolerance policy.
'As soon as we see them or they are reported they will come down.' said a spokesman for the council.
'We urge residents if they see them go up again somewhere else to let us know and we will get rid of them.'
Deputy Prime Minister Nick Clegg attempted to save face with his backbenchers by having the control order regime watered down and re-named Terrorism Prevention and Investigation Measures, or T-Pims.
Mrs May has been told about the posters by Sadiq Khan, MP for Balham and Tooting.
A spokesman for the Home Office said: 'We are aware of the posters but we never comment on matters of the Home Secretary's personal security. It is a matter for the police.'
Scotland Yard is trying to trace the people behind the posters.
'We are aware of the posters and we have liaised with the local authority as to their removal,' said a spokesman for the Metropolitan Police. Inquiries are ongoing.'
It is unclear how seriously the Home Office and Scotland Yard are taking the posters, given that a fatwa can be interpreted as an incitement to murder.
The author Sir Salman Rushdie was the subject of a fatwa issued by Iran's Ayatollah Khomenei in 1989 after the publication of his book Satanic Verses.
The author said the threat comes in the form of a 'sort of Valentine's Day' card each February 14th.