Schools are being urged to avoid branded uniforms and allow parents to “shop around” to cut costs for cash-strapped families.
Schools minister David Laws said the cost of clothing was often “unnecessarily high” at a time when family budgets were being squeezed.
An Office of Fair Trading investigation last year suggested that three quarters of schools placed restrictions on where uniforms could be bought.
That typically added £5 to the price tag for each item, leaving parents an estimated £52m a year worse off.
Mr Laws announced the new guidance for schools at the Liberal Democrat conference in Glasgow.
Exclusive single supplier contracts should not be used, unless regular tendering processes are run to ensure firms provide value for money.
They should also not enter into ‘cashback’ agreements with shops.
Compulsory items of uniform should be available relatively cheaply, and branding should be kept “to a minimum”, under the guidelines.
Schools are urged to avoid changing specifications frequently.
Mr Laws told Sky News the revised guidance on uniforms would end the “over-reliance” by schools on single supplier agreements.
“It ought to be possible for parents to shop around, to get good quality school uniforms but from different suppliers,” he said.
“Schools should avoid changing their school uniforms too often and requiring parents to buy different items.
“They ought to keep in mind what is specified in a school uniform and keep it as cheap as possible.
“And they ought to enable standard items like trousers and shirts and so forth to be bought from some of the big supermarkets and other shops where actually those items can be bought very cheaply.
“I think schools can actually do this and give parents a better deal but without actually compromising on quality.”
Asked why the guidelines were not being pushed further, the minister said he did not think it was necessary for ministers to legislate and “set out hundreds of pages of bureaucracy in order to get schools to do what is the right thing”.
He said he expected schools to follow the guidance, but if they failed to, the Government would respond to parental complaints.
According to an Ipsos Mori put out by Mumsnet, female support for the Lib Dems has fallen by 15% since 2010.
Asked if the move was a bid to win the female vote at the next general election, Mr Laws said households were facing “living cost” challenges across the country and that his party would be making a series of announcements this week on “actions that we are going to take to help hard-pressed families”.
Sky’s Anushka Asthana said: “The Lib Dems are putting this out today in an attempt to appeal to parents and to say they are on the side of struggling families.”
“What the Government wants to see is policy where uniforms can be bought anywhere – at supermarkets or at the more expensive suppliers.
“It is part of what they are doing here at Glasgow, which is trying to say that in government, despite only having 57 MPs, they are having an impact and their policies are pushing through.
“But there is a lot of debate whether this policy will make much difference,” she added.
Stephen Twigg, shadow education secretary, said: “Labour have been calling for action on school uniform prices to deal with the cost of living crisis. Yet the Lib Dems have done nothing for three years.”
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