'I defaced £50m Rothko work – but I'm no vandal'

The man who scribbled on a Mark Rothko painting this week wasn’t your ordinary vandal (TIM WRIGHT)

An artist has claimed responsibility for defacing a £50m Mark Rothko mural at the Tate Modern gallery in London – but denied he is a vandal.

Police are investigating after the Russian-American expressionist's work, Black On Maroon, right, was daubed with black paint on Sunday by a man who wrote in one corner of the picture: "Vladimir Umanets, A Potential Piece of Yellowism." Last night, Mr Umanets admitted writing on the work but insisted: "My intention was not to destroy or decrease the value, or to go crazy. I am not a vandal."

Mr Umanets, who studied art, is a founder of "Yellowism", which he described as "neither art, nor anti-art". "It's an element of contemporary visual culture," he said. "It's not an artistic movement. The main difference between Yellowism and art is that in art you have got freedom of interpretation,. In Yellowism you don't have freedom of interpretation, everything is about Yellowism – that's it. I am a Yellowist. I believe what I am doing and I want people to start talking about this. It was like a platform."

Mr Umanets, who would not reveal his age or where he lives, said he knew he was likely to be arrested but added: "I believe that from everything bad there's always a good outcome, so I'm prepared for that. Obviously I don't want to spend a few months, even a few weeks, in jail. But I do strongly believe in what I am doing; I have dedicated my life to this."

Last night, police said they were pursuing several lines of enquiry.