Parents across Britain will be asked to pay significantly more for their children's school dinners from Monday, in a move that experts say will lead to thousands of poorer pupils missing out on healthy meals. Prices will rise by up to 17% in some schools, with charges set to exceed £2.60 in the most extreme cases.

The higher charges come amid soaring food costs and in response to the government's decision to remove protection for a subsidy that has kept prices low in recent years.

The school dinner grant loses its ring-fencing on Monday and can be spent by schools or local authorities to cover gaps in other budgets. The Observer has learned that more than 30 local authorities intend to increase the cost to children in coming months.

Writing in today's Observer, chef and food campaigner Jamie Oliver says he hopes the government will continue to invest in "quality school food, and the integral support and training of kitchen staff". He writes: "I believe that any compromise on a child's right to a healthy school lunch... is child abuse on an unimaginable scale."

Doncaster council will increase the price of a lunch by 17% tomorrow to £2.10. By the end of the month, Lewisham plans to raise its prices by 14% to £1.60 and Blackpool is planning a 7% rise in the next academic year to £2.10.

Bolton council has announced that it will scrap its hugely popular £1-a-meal policy in September and increase the price to £1.50 by January next year.

Schools that have taken over responsibility from local authorities for providing meals to pupils are also expected to increase their prices.

In Poole, the council said that the average price charged by schools would rise by around 11p to £2.50 in this financial year. In Somerset the price in some schools recently increased to £2.60 and could rise further. Meanwhile, six meals services in the area have closed because their future was deemed financially unviable. It is feared that more schools plan to stop providing hot meals. Wendy Green, the council's transforming school food project manager, said she had concerns for rural schools where delivery costs were an added expense. "These services are going to struggle with the loss of that funding. Four years ago we only had hot meals in 30% of primary schools, now we have them in 80%. My concern is that we are going to start dropping back below 80%. Our prices are variable, but most are charging between £2.25 and £2.60 for a two-course meal for a primary school child. That's a lot of money for a family with two or three children. If it doesn't go on the meal price, parents could be faced with a significant hike. A lot of parents won't be willing to pay that and then those services will not be viable because the uptake will be low."

Research from the Schools Food Trust shows that the uptake of school meals is sensitive to price changes. A paper commissioned in 2009 suggests that a rise in the price of a school meal prompts a corresponding fall in take-up. Carmel McConnell, from the child nutrition charity Magic Breakfasts, said she feared an escalation in malnutrition in schools. She said: "I think we will see more cases of scurvy and other conditions."

Children eating healthy school dinners promoted by celebrity chef Jamie Oliver six years ago enjoyed dramatically improved test results, according to research undertaken by academics at Oxford and Essex universities.

The chef's nutritious meals were more effective than the government's daily literacy hour at raising standards of English in primary schools. Where healthy meals were eaten there was a rise of 4.5% in English Sats results in the first schools where the scheme was tried. This compared with a 3.2% rise linked to the introduction of structured daily literacy lessons. Pupils took less time off sick.

For his Jamie's School Dinners series in 2005, Oliver visited a school in Greenwich, south-east London, and insisted that it scrap Turkey Twizzlers and chips in favour of nutrient-rich foods such as fish and broccoli. This spawned the Feed Me Better campaign with the wider goal of improving school dinners.

The price rises will affect any child whose parents collectively earn more than £16,000 a year, the threshold for a free school meal.

A spokesman for the Department for Education said: "We make no apologies for giving headteachers complete freedom over their budgets – they know what's best for their pupils. The tough nutrition standards remain in place."

Jamie Oliver

Sadly, politicians can have short memories. Back in 2005, when I took the school dinners petitioned to Downing Street, members from all parties were queuing up to say how school dinners needed to be radically improved and how important investment and a long-term food strategy was.

Parents, teachers and the media across the country were shocked at the standard of food their kids were being fed 190 days a year from the ages of four to 16, during – the most precious years of their lives. We all fought hard to get new money injected into the system.

I had a positive meeting with Michael Gove before Christmas, and for the country's sake I hope he ensures the continued investment in quality school food, and the integral support and training of kitchen staff where needed.

Food education in schools is also incredibly important. It was made compulsory for children in secondary schools in 2008, and is only due to come into schools this September. But already it is now under threat of being removed from the curriculum completely.

It's the long-term health, happiness and productivity of the future of our country that is at risk. I believe that any compromise on a child's right to a healthy school lunch or their access to learning about food, where it comes from and what it does to their body is child abuse on an unimaginable scale.

Credit to Labour for justly pioneering the school food changes. I hope that the coalition government will only improve on what they (the previous government) started.