Halal lamb burgers have been removed from 19 city schools after tests revealed pork in a sample burger.
Traces of pork were found in the frozen product supplied by Doncaster-based manufacturer, Paragon Quality Foods Limited following DNA tests conducted on behalf of Leicester City Council.
The burgers have been on Leicester school menus since January this year and are the only product supplied to the city council by the firm.
Councillor Vi Dempster, assistant city mayor for schools, said she was "appalled by the situation."
Coun Dempster said: "The council took immediate action when it was discovered and the product was withdrawn from school menus immediately ahead of further tests being carried out. We will not be using this company again.
"It's disgraceful that none of us can have confidence in the food we eat. We regret any distress this will cause families and staff, and would like to reassure them that robust action is being taken to address this serious matter."
Regular tests have been carried out on behalf of the council since the horse meat scandal in February when traces were found in beef products across the country.
The council was informed of the results on April 18 and says it withdrew the product the following day to await further tests.
All other Halal products used in the council's kitchens are supplied by another company, The Punjab Kitchen Ltd, based in Tyneside. Tests have shown that they are Halal compliant.
Education bosses have sent out 6,000 letters to parents and head teachers at the affected schools this week to tell them about the situation.
Trevor Pringle, the city council's director of young people's services, said: "We will not be purchasing any further products from this supplier and we have made it clear to all our suppliers that this is totally unacceptable. We are taking urgent legal advice about the next steps."
The Food Standards Agency has been notified of the contamination, along with local authority bosses in Doncaster.
Taylor Road Primary, in St Matthews, Leicester, is among the schools which received the lamb burger
However, head teacher Chris Hassall, said that it had not been served in school since March.
He said: "The horse meat scandal made me very cautious about the food we were serving in school and regardless of its halal content, we did not consider it to be the healthiest option - therefore it was removed from our menu.
"I eat school dinners myself everyday and I want to be assured that children are receiving nutritious food that is what it says it is.
"I'm pleased that we took our own precautionary measures and that Leicester City Council has been pro-active enough to carry out tests since this scandal immerged.
"Muslim parents need to have confidence in school food and the council has been absolutely transparent about its findings."
The council has been working with the Federation of Muslim Organisations (FMO) as part of its investigations.
Suleman Nagdi from the FMO said: "This is a shocking and unacceptable development. As Muslims, we cherish our strict dietary needs, which are well known and have been developed for well over a thousand years. The consumption of pork and alcohol is prohibited for all Muslims.
"This recent event will raise an issue of confidence in our community as to the measures and processes that are put in place that gives assurance of Halal meals. All due diligence procedures should be thoroughly reviewed and bolstered where necessary and should include intermittent and random sample testing which should encompass DNA testing.
"It's hoped that this will not occur again and the community are now looking to the city council and our elected councillors for this assurance and to rebuild the confidence that has clearly been shaken."
The federation has also urged the council to take legal action against the company concerned.
Mr Nagdi added: "We feel that such a prosecution would be in the public interest and would send a clear message to all businesses in this sector that contamination will not be tolerated."
For a list of schools affected click hereclick here
