A former education adviser to Tony Blair has claimed the Conservatives are likely to be flooded with requests from "religious sects and cults" to set up academies should the party come to power next year.
Conor Ryan, who acted as adviser to both Mr Blair and former schools secretary David Blunkett, and was also a key figure in the creation of the academy programme, believes the Tories' plans could see a proliferation in requests from "less desirable" religious groups.
A cornerstone of the Conservatives' proposals for school reform is to give parents more choice and more power when it comes to deciding where they send their children to school.
Michael Gove, shadow schools secretary, has pledged to allow any interested party, from charities to parent groups, to apply to open a new academy-style school.
But Mr Ryan thinks it doubtful that groups of parents will have the time or the inclination to open new schools, creating the possibility for more faith schools to step in.
"It is unlikely that there will be huge numbers of parents using the powers to set up new schools," he said, "but the change in the rules will mean we will see new schools, particularly faith schools, applying and opening up.
"This will mean the government will have to avoid a great deal of applications for undesirable religious schools from cults and sects, which they would not want."
The National Secular Society (NSS) said it had already raised the issue with Nick Gibb, shadow schools minister, more than a year ago.
Keith Porteous Wood, NSS executive director, said: "From our perspective there's a danger that sects, other religious groups and more mainstream religions will open up schools despite there being a decline in religious attendance. It will simply restrict the choice of parents who want their children to go to a good school that isn't of any religious denomination.
"This whole policy seems to be based upon allowing parents more choice, but I don't see how it delivers it. We are going to have Moonies, Jehovah's Witnesses - name the sect - carpetbagging local education funds at the exclusion of other people who don't have the ability to form their own pressure groups."
The current academy programme has already led to a marked increase in faith groups running schools with approximately a quarter of academies being operated by religious organisations.
The Conservatives said any group wishing to open an academy would have to face close scrutiny in order to receive funding.
A Conservative spokesman said: "As with current academies, all new schools would have to enter a funding agreement with the department.
"Clearly the department would not approve funding agreements that would allow cults or religious sects to open up schools."