Jamie Oliver became something of a national treasure when he marched into school kitchens and revealed the grim secrets of Turkey Twizzlers and chips with everything.

The Return of Jamie Oliver will hit TV screens on September 18, and the celebrity chef was promoting his school dinner campaign once again yesterday at Channel 4 headquarters in London.

A year on from his series exposing the state of school meals, Oliver has gone back to see whether things have improved. As with politicians everywhere, he found that launching initiatives can be easier than delivery.

In the first series, Oliver took over school meals in Greenwich, south-east London, teaching dinner lady Nora Sands of Kidbrooke school to cook healthy meals. He also extracted a promise of £280m new money from the government to raise nutritional standards around the country, following a campaign and a petition which attracted 300,000 signatures.

Returning to Kidbrooke, Oliver heard from Ms Sands that the new funds only delivered just over £2,000 directly to her catering budget. Take-up of school meals is down 2% nationally since the series, making it harder for schools to cover overheads while providing hot meals. At Kidbrooke, the meals service has fallen about £15,000 into deficit, partly because it is no longer making money out of selling sweets and snacks and partly because it no longer supplies meals to local primary schools.

Oliver's frustration was evident at a press conference yesterday. He said that 70% of the lunchboxes he had seen while making his programmes were inappropriate. He said he would like to see lunchboxes banned if there were a good meal service. "I have seen kids of the ages of four or five, the same age as mine, open their lunchbox and inside is a cold, half-eaten McDonald's, multiple packets of crisps and a can of Red Bull. We laugh and then want to cry."

Oliver visited Alan Johnson, the third education secretary he has dealt with in the course of making the programmes. Unable to win an assurance that money for new kitchens will be ringfenced, he petitioned the prime minister.

At a meeting on July 18, Tony Blair promised to set up a new trust fund for kitchen building and to commit a further £240m to healthy ingredients once the original funding runs out. The Department for Education and Skills announced on Monday that additional money would be available.