Parents will not be consulted if schools decide to select on aptitude for sport, the performing arts, visual arts, modern foreign languages, design and technology or information technology.
Only "admissions authorities" - church schools, former grant-maintained schools and the local council - would have that right.
The ruling, contained in the admissions code of practice has prompted fears that groups of schools will work together to introduce selection.
Three years ago, 13 grant-maintained secondary schools in the London borough of Bromley introduced partial selection causing serious admissions problems.
Some children found themselves without a school place on the last day of the summer term. More than 19 per cent of pupils at Bromley schools are from outside the borough.
More problems are expected in councils with large numbers of opted-out schools. Margaret Tulloch, from the Campaign for State Education, said:
"The worry is that, like in Bromley, schools could work as a group, possibly with the acceptance of the LEA and parents won't have a say."
The code of practice will affect admissions from the September 2000 intake and gives parents the right to object to existing partial selection on aptitude. This opens up challenges in areas like the London borough of Wandsworth, where neither the council nor schools are likely to protest.
Campaigns are already being devised, and schools being targeted include Ernest Bevin and Graveney, which select 50 per cent, and Burntwood, which selects 30 per cent. All are GM schools.
Ministers have said that there will be no more selection by ability but that schools can select up to 10 per cent of pupils on aptitude.
Martin Rogers, of The Education Network, said: "It all boils down to semantics. There is a danger of using aptitude as a smokescreen for testing ability by proxy."
The Chambers English Dictionary defines "aptitude" as natural ability and "ability" as the quality or fact of being able.
Liberal Democrat education spokesman Don Foster is to object to the code of practice in Parliament and yesterday Government whips were discussing the timing of the debate.