Osborne, now editor of the Evening Standard, is said by Esquire magazine to have mentioned the phrase to more than one person at the London newspaper.
It would not be the first time he has used gruesome language about May, who sacked him as chancellor when she succeeded David Cameron after the EU referendum.
He has previously described May as a “dead woman walking” who is on “death row”, while an Evening Standard leader compared the prime minister to the “living dead in a second-rate horror film”.
Since Osborne became editor, the newspaper has carried scathing news articles and leaders about May’s approach to Brexit and her stewardship of the Conservative party.
Osborne has not commented on the claim although he was active on Twitter on Wednesday. His office has been contacted for comment.
His remarks provoked criticism from some of his former Conservative colleagues. Nadine Dorries, a Tory MP who once described Osborne and Cameron as posh boys who did not know the price of milk, said it was “a brief insight into how his mind works and always has”.
Nick Timothy, May’s former co-chief of staff who resigned after the election, highlighted the quote on Twitter, along with remarks by an ally saying: “He’s got a gun now. One thing people in the Conservative party will realise is ‘you mess with George Osborne at your peril’.”
In an apparently sarcastic follow-up tweet, Timothy added: “Not sure why he worries people think he’s an arsehole.”
Asked for the prime minister’s reaction, her official spokesman said: “The contents of the former chancellor’s freezer are not a matter for me.”
This article was written by Rowena Mason Deputy political editor, for theguardian.com on Wednesday 13th September 2017 13.23 Europe/Londonguardian.co.uk © Guardian News and Media Limited 2010