Private-sector caterers have reacted angrily to claims that they are using Private Finance Initiative (PFI) contracts to undermine improvements in the standard of school meals, but parents remain unconvinced.
Last week newspaper reports claimed that long-term contracts with private-sector caterers were blocking plans to improve standards because schools lacked bargaining power under the lengthy terms of PFI contracts.
In the south London borough of Merton, six secondary PFI schools are committed to 25-year agreements with a firm called New Schools, which has subcontracted catering to Scolarest, part of catering giant Compass.
But a parent pressure group has claimed that the contract prevents both parents and schools from improving the quality of school meals in the region, which they feel is inadequate.
Chris Larkman, chairman of the group and a parent governor at one Merton school, said that the local authority was failing in its duty towards children in the borough.
"Our first demand is for the local authority to recognise the appalling quality of meals in our schools and the poor way in which the lunch arrangements are set out," he said.
"We're very happy to work with Scolarest but the reality is that we feel the apparently good contacts between the council and the caterers don't result in good food on our children's plates. What we're looking for is fresh produce prepared on site like they're now getting in Greenwich."
About 250 parents and children staged a demonstration for better school meals outside the civic town hall in Morden last Friday.
But Scolarest and Merton council claimed there was room for negotiation over what goes on children's plates.
A spokeswoman for Compass said: "There are no contractual terms within a PFI contract, or any other type of contract we operate, that would hinder or prevent us from continuing to develop and evolve the menus and service within schools."
A spokesman for the local authority said Scolarest currently spent 65p per head on secondary school meals but discussions with the caterer were ongoing. "At the moment we provide a buffet-style dining service but parents are arguing that there should only be healthy options on the menu," he said.
He also admitted that at least one school in the borough served chips five days a week.
A statement from Merton Council leader Andrew Judge said: "The food offered to children is balanced. Pupils may choose an unbalanced mix from the menu options, but this is difficult to prevent without restricting choice. Chips remain popular with children, as always."
According to the Department for Education and Skills there are now about 65 school PFIs in the UK, which cover about 680 schools with a capital value of £2.6b.