The Local Government Association warns that many schools are forcing parents to shell out hundreds of pounds for new uniforms after gaining academies status.
This term alone, at least 275 schools will convert to academy status while more than 100 others are in the process of applying.
Many use the move to make a clean break from the past, including a new name, logo, motto and revamped uniform.
But the LGA said it left many parents having to pay “hundreds of pounds all at once, to replace clothes which there is nothing wrong with”.
It is now calling on schools to adopt a “common sense approach” to uniform policies, by keeping to a similar colour scheme or giving parents the chance to simply sew or iron new badges onto existing clothes.
The conclusions follow claims last year from David Laws, the Schools Minister, that the cost of clothing was often “unnecessarily high” at a time when household budgets were being squeezed.
Research shows that the average family with two children currently spends £450 on uniforms, coats and bags, with prices increasing by more than 40 per cent in a two-year period.
Guidance issued to schools says exclusive, single supplier contracts should be banned and compulsory items of uniform should be available relatively cheaply on the high street.
But the LGA claim that many schools with academy status are placing unnecessary demands on parents. Academies are state schools that are run independently of local council control, with more freedom to alter the curriculum, admissions, staff pay and the shape of the academic year.
A recent report by the charity Family Action found parents were paying an average of £161 for boys and £156 for girls in secondary schools, while primary uniforms cost £113. But it found evidence of schools asking more when they make the transition to academy status.