As many as 3,000 schools have broken the new admissions code, with ministers revealing that some are charging parents hundreds of pounds for what is supposed to be a free education.
Spot checks on three local authorities - Barnet, Manchester and Northamptonshire - uncovered the practice, which Ed Balls, the Schools Secretary, said was unacceptable and likely to be more widespread.
"In a number of cases, the requirement for a financial contribution ran into many hundreds of pounds a term," he said.
"In one case, parents were required to fill in a standing order or to make a cash or cheque payment as a condition of returning the application form."
Barnet council in north London is talking to four Jewish primaries and one Catholic primary, which the authority says have asked parents about making financial contributions on their admissions application forms.
Hasmonean Primary is the only one to have been named after asking parents for a pound;50 "admission fee" on its application form.
The state-funded Jewish school says the term on the form is incorrect and actually refers to a "deposit" that parents send, and has no bearing on pupil admission.
Forms from three other primaries asked about voluntary contributions towards the cost of Jewish studies and security - some Jewish schools are now fitting bulletproof and explosion-proof windows.
A Barnet Catholic primary's form asks whether parents are able to contribute to a governors' fund towards maintenance of the school.
Mr Balls said other illegal admissions practices uncovered, mainly in faith schools, included interviewing children, asking about parents' marital, occupational or financial status, and not giving looked-after children priority.
A spokesmen for the Catholic Church and the Board of Deputies of British Jews said they were committed to ensure there was full compliance with the code.
Ministers appeared to blame schools and local authorities for the illegal practices. However, campaigners pressed the Government to amend the Education and Inspections Bill to give local authorities the duty to produce an annual report stating whether or not schools in their areas complied with the code. At the time, they rejected the idea as unnecessary, but this week Mr Balls said the law would be amended to "place a further duty on local authorities to report each year on the legality, fairness and effectiveness of all school admission arrangements in their area".
TOUGHER PATROL OF THE CODE
- Local authorities to report each year on the legality, fairness and effectiveness of all school admission arrangements in their area.
- Everyone with an interest in admissions policies to be consulted.
- Guides for parents on admissions and appeals codes to be published.
- The period in which parents and local authorities have to object to admissions arrangements to be extended from six to 16 weeks.