Jamie Oliver is urging ministers to put more money into school meals as official figures show growing numbers of pupils are eating the healthy dinners his campaign inspired.

The benefits to children's health should prompt more government investment, said Oliver. Short-term financial pressures should not threaten the provision of nutritious school food, he added.

He spoke out after data from the government's School Food Trust showed the number of pupils in England eating a hot lunch at school had risen by 320,000 in the past year – an increase for the third consecutive year.

The figures contradicted health secretary Andrew Lansley's assertion last week that take-up had fallen since the quality of school meals was radically overhauled after Oliver's Jamie's School Dinners series in 2005. The programme revealed that many children were being fed chips and Turkey Twizzlers.

"Some people in government might look at the figures and think that it's now time to take the foot off the gas because it's a success story. That would be completely wrong," said Oliver. "Now is the time to move up a gear. This is the time for education and health departments to invest in those schools who still have problems with lack of training for dinner ladies or who suffer from having a dining area that's too small or uninviting."

He asked ministers not to let the progress made in pupils' eating habits be lost. "Investment now saves lives and [the] NHS billions in the future. We're on the right track with school meals. We can't allow anything to slow this down," he said.

But the Department for Education has refused to promise to extend the £80m-a-year subsidy, the school lunch grant, it gives local councils to help them provide the healthy school meals Labour introduced. It is guaranteed until the end of March 2011.

"All future spending decisions for after 2011 will be part of the comprehensive spending review in the autumn and we can't pre-empt the decisions or content," a spokeswoman said.

"Ministers want school in food to remain healthy and will set out decisions in due course."

The Liberal Democrat children and families minister, Sarah Teather, added: "We welcome the increase in the number of children getting a healthy meal in schools. We want to ensure school meals continue to be healthy and will set out the next steps for school food policy in due course."

The Children's Food Campaign wais concerned that widespread cost-cutting in Whitehall could risk future funding, making it difficult for councils to produce healthy meals at affordable prices.

The National Obesity Forum spokesman, Tam Fry, said Lansley should stop denigrating Oliver's campaign.

School meals in England are backed by legal standards requiring them to include a certain amount of carbohydrates, vitamins and minerals, and restricting the amount of fat, salt, sugar and saturated fat they can contain.

A Department of Health spokeswoman said that contrary to media reports, the health secretary had applauded Oliver's campaign when he addressed the British Medical Association's annual conference. He criticised Labour government restrictions on the campaign.