Rule number one for art lovers of any age: Don't touch the sculptures at the museum. One couple broke that cardinal rule on Sunday by allowing their children to crawl all over a multi-million dollar sculpture at Tate Modern in London, to the horror of the Internet.

Visitor Stephanie Theodore, a visiting gallery owner from Brooklyn, New York witnessed the children clambering over the installation by American artist Donald Judd and snapped a photo of the scene, posting it on Twitter with the caption, "Holy crap. Horrible kids, horrible parents."

"I was shocked," Theodore told the U.K. Standard. "I said to the parents I didn't think their kids should be playing on a $10 million artwork. The woman turned around and told me I didn't know anything about kids and she was sorry if I ever had any."

Ms Theodore alerted Tate guards but the family had walked away. "I don't know who they are but I just know you don't put your kid on a sculpture. It wasn't just the kids, the parents were encouraging them … It isn't about monetary value, it is a museum, not a playground."

A representative from Tate Modern emailed the following statement to Yahoo Shine: "Tate welcomes families to all of its galleries. On Sunday 26 January 2014 at 17:30 a child lay on the bottom part of the Donald Judd sculpture Untitled 1980. The situation was dealt with immediately. There is always risk of damage when visitors touch works of art, but the sculpture has been checked by Tate's conservation team and no damage has been caused on this occasion."

