Staff involved in the trashing of an iconic Melbourne store during an unauthorised Christmas party have escaped criminal charges.

Around 20 staff, both past and present, joined the impromptu after-hours Christmas bash at Dimmeys store, in Swan Street, Richmond, on Saturday night.

Things quickly got out of control when staff began damaging stock, breaking windows, and covering the whole shop floor in fake snow.

Police busted the party shortly after midnight, arresting three men and two women who were later released without charge.

Staff at Dimmeys store in Richmond threw an unofficial Christmas bash that turned to trash. Photo: 7News

The party antics, captured on CCTV, was condemned by management and it is understood one worker is facing the sack.

Store manager Loulla Theodosi said: "The store was in a mess. There was broken glass everywhere and stock damaged.

"I couldn't believe it happened. I thought it was someone playing a prank.

"They are lucky they work for a good company and the bosses are great guys.

"However, it shouldn't have happened. We're just happy that no one got hurt."

Stock was damaged and windows smashed during an unofficial staff Christmas party at Dimmeys store, Richmond. Photo: 7News

Staff say they threw the party to celebrate 'an end of an era' at the Richmond store, with the site set to undergo extensive redevelopment next year.

One staffer Crosley Querin, who was one of the 20 casuals who took part in the illicit bash, told Seven News: "It was a great night. There were a few little mishaps at the end. There was no breaking and entering, there was internal stuff that was wrong but no criminal problems.

"I think it was blown out of proportion. When someone left a window got broken. For 95 per cent of it we had a good time."

The aftermath of an authorised party at Dimmeys store in Richmond. Photo: 7News