Tough new rules on admissions will put the onus on individual schools to ensure their policies do not lead to social segregation.
A draft code on admissions also warns schools against expensive uniforms or prospectuses mentioning parental contributions for school funds or trips, which could discourage poorer families from applying.
The code, released to MPs considering the education Bill, targets back-door selection and is part of a series of concessions aimed at minimising a future Labour backbench rebellion.
Heads have already said that the code is unworkable. It is due to come into force in 2007 and schools will have to "act in accordance with" rather than just "have regard to" it.
For the first time, it sets out a list of don'ts for oversubscribed schools deciding between pupil applications. These include not taking into account primary school reports on a pupil's behaviour or attitude, their family's behaviour or their parents' occupation or marital status.
Schools which control their own admissions - foundation, voluntary-aided and new trust schools - will have to show that they are taking steps to reduce segregation.
They should: "Analyse information about their intakes, and where possible their applicants, to find out whether they attract a wide range of families or whether their school fails to attract all sections of local communities.
"They must act upon this information if any of the schools or admission authority's policies or practices are likely to be at fault."
The code suggests that the most popular schools could work with primary schools in more deprived areas to encourage applications from poorer families.
It adds that faith schools should work with local primaries to encourage "local people of the faith - or of other or no faith" to apply.
The code also also warns that low-income families are often concerned about the price of uniforms. Schools where the cost of the uniform, including sports kit, is above the national average are expected to have schemes in place to help pay the bills.
A 2003 study commissioned by Norwich Union found that on average parents spent pound;178 a year on uniform - pound;172 for primary pupils and pound;185 for secondary.
The code says schools can help by ensuring that the uniform chosen is widely available in high street shops or on the internet rather than "an expensive sole supplier". It says they should not try to raise extra funds through uniform sales.
John Dunford, general secretary of the Association of School and College Leaders, described the code as "all things to all people", adding: "It sounds good politically but I think it is completely unworkable."
Barry Day, head of Greenwood Dale, a foundation school in Nottingham, said the code would be impossible to administer.
"We are an inner city school and give priority to local children which means our intake is skewed away from the middle classes," he said.
"By taking action over an initiative which calls for a wide range of families, we would be disadvantaging local youngsters and bussing in the middle-class pupils from outside. That would be social engineering gone mad."
But Philip Hunter, chief schools adjudicator, whose office will decide over disputes when schools are accused of breaking the code, did not anticipate problems.
"Adjudicators have got used to the idea of reading the words in the code and making judgements about them," he said.
"That is our job. This code presents a very robust means for making sure that heads observe it and is a good deal more directin making sure they don't select."
MUST-NOTS FOR OVERSUBSCRIBED SCHOOLS
If your school is oversubscribed, DON'T:
* Give higher priority to children whose parents are more able or willing to support the school's ethos, or support it financially.
* Prioritise children according to the occupational or financial status of parents, their educational and social backgrounds or marital status.
* Take into account reports from a child's primary or nursery school about past behaviour or attitude.
* Favour those whose siblings or relatives are former pupils.
* Take account of the behaviour of other members of a child's family, including records of attendance.
* Give priority to pupils whose parents are staff, governors or have another school connection.
* Prioritise children with particular interests, specialist knowledge or hobbies.
* Decide according to the order in which applications were received.
* In the case of grammar schools, prioritise siblings of pupils.