Healthy food reforms were "blown up" by Brexit and then pushed out by Theresa May, Jamie Oliver has said.
The celebrity chef called on the Government to take a "sterner" approach to tackling childhood obesity and called for a ban on TV junk food advertising to be extended to 9pm.
Oliver said he had been getting his "hands dirty" by trying to change eating habits in the most unhealthy parts of the country.
He is giving evidence alongside Hugh Fearnley-Whittingstall to MPs on the Health and Social Care Committee on Tuesday afternoon.
Oliver has previously faced criticism over comments he made about families eating chips and cheese out of Styrofoam containers in front of a large television.
Asked about the remarks, he told BBC Radio 4's Today programme: "I've learnt a lot in 15 years and when I talk to a lot of people I have tried very, very hard to get my hands dirty, work in the most unhealthy parts of the towns."
Oliver had pushed for former prime minister David Cameron to introduce reforms to tackle childhood obesity but accused successor Mrs May of halting progress.
The Commons session comes ahead of the next chapter of the Government's Childhood Obesity: A Plan For Action, which is expected this year.
He said:"What we need is an environmental change where everyone does their bit, civic, government, business, the home.
"I worked with Mr Cameron within his group to formulate chapter one, which of course, with Brexit and everything that happened got blown up.
"Mrs May took over, they pushed it out."
He said: "It's now time for a much sterner, broader, intelligent and strategic attack on childhood obesity."
Oliver said buy one, get one free offers were designed to make people eat more.
"If you're skint, it is really tough," he added.
Other witnesses facing the committee include academics, health and fiscal experts, who will give their assessment of the Government's performance in this area, and say what they expect from the next part of the plan.
Last week the Prime Minister described the UK's plans to tackle childhood obesity as "ambitious" and "world-leading", but she added that further action has not been ruled out "if the right results aren't seen".
Oliver has long been a campaigner for healthy eating, particularly when it comes to children.
His fellow chef has a new BBC series out, Britain's Fat Fight With Hugh Fearnley-Whittingstall, looking at why people are eating so much.