Osborne became well-known and was often mocked for appearing in PR pictures in similar outfits.
"We're all builders now," May declared, as she accepted the Politician of the Year gong from her former cabinet colleague.
The prime minister also used her speech to launch a scathing attack against Sir Craig Oliver, a former BBC journalist who served as Cameron's director of communications and recently published a book about the EU referendum campaign.
"I'm particularly pleased to see Craig Oliver is here tonight. Sorry, Sir Craig..." May said.
"I understand that in his book... [he] says that when he heard the result of the referendum he walked out of the office, walked into Whitehall and started retching violently.
" I have to say I think we all know that feeling....Most of us experienced it too when we saw his name on the resignation honours list."
Boris Johnson, a former editor of The Spectator, also addressed the politicians and journalists.
The foreign secretary said the UK would make a "Titanic success" of Brexit, unintentionally drawing a comparison the 1912 sinking of the passenger liner.