The School Food Trust (SFT) has hit back at claims by the Local Authority Caterers' Association (LACA) that new rules governing the provision of food in schools have driven some caterers to the brink of collapse.
According to LACA, take-up of meals in secondary schools has slumped 17% since 2004.
But an SFT spokesman said: "We will be publishing our own independently run annual take-up survey of local authorities across primary and secondary schools in England in August.
"Initial analysis suggests our results will be different from LACA's. By our reckoning, the take-up in primary schools has remained pretty constant. In secondary schools, take-up is down 5.3%."
The spokesman acknowledged that secondary schools were proving "tougher nuts to crack than primary", but said the SFT was confident the situation would improve over time. "It's mainly the 15 and 16-year-olds that are having trouble adjusting."
In the meantime, most local authority caterers were now operating at a loss, claimed Joe Hunt, regional chairman for LACA in the north-west. "This is clearly not sustainable," he added.
Although more government cash had been pumped into school meals, it was proving extremely hard to find healthy and appealing products within what was still a very tight budget, said Hunt.
"It's all happened very fast and many manufacturers haven't had enough time to prepare."
A ban on all fizzy drinks (including diet variants) and bagged snacks (except nuts, seeds and dried fruit) would hit school revenues further when it came into force in September, he said. "How many 15-year-olds want to eat a bag of pumpkin seeds at break-time?"
But Hunt welcomed recent moves to allow schools to spend money previously earmarked for ingredients on other things, such as equipment or staff training.