The TV star and restaurateur has been highly critical of the Prime Minister’s approach to tackling childhood obesity and the now-shelved plan to scrap free school meals for infants.
Oliver said May’s administration was “completely locked down” with her team of close advisers keeping information away from ministers.
The PM’s reliance on close aides was criticised in Tory circles following the election, leading to the resignations of joint chiefs of staff Nick Timothy and Fiona Hill.
Oliver blamed May’s team for watering down the childhood obesity strategy that David Cameron’s government had been working on.
The strategy, published in August 2016, stopped short of ordering restrictions on advertising and promotional deals on junk food which campaigners had called for.
Oliver told the Sunday Times magazine: “Look, I have met four prime ministers. They are all very different, but ... May’s government was completely locked down.
“Her advisers, that have now gone — thank you, Lord — kept all the information away from even their own ministers.
“It (the strategy) was released at the same time the A-level results came out, with no marketing, no comms, no PR. In code, that means, ‘We don’t give a f***’. It was unbelievable. Blatant.
“I had been working intimately with Mr Cameron and his group. It could have been a moment of national pride and at least she would have been able to look everyone in the eye and say we are going to get some change in the obesity graph in 10 years.”
Instead, May “tore it up”, acting in an “awful” way, Oliver said.
“But what’s even more scary ... is that when May released the child strategy that she had ruined, I believe her team were genuinely chuffed with what they had done.”
After losing her Commons majority in the election, Tory plans to scrap free school meals for infants in England were dropped.
Oliver said the policy was “like something a 10-year-old would do in basic maths to save cash”.
The chef said the Tory manifesto amounted to “we are going to stitch up the old, stitch up the young and we are going to bring back fox-hunting” - but he did not back Jeremy Corbyn’s Labour either.
He would not be drawn on how he cast his ballot in the General Election, “but I didn’t vote Conservative and I didn’t vote Corbyn”.
Oliver, who has previously made a point of not voting in general elections because he did not want “my political things to sway my ability to make changes” with any party, said he did take part in this year’s contest.
“I did vote this year and I voted because it was a protest vote,” he said.