A tagger who graffitied the top of a central Christchurch tower caused more than $25,000 of damage, breaking through four wooden hoardings and smashed locks with a sledgehammer.

The owners of the former Forsyth Barr building this week started to clean the giant tag reading TOGO from its makeshift canvas more than 70 metres above the city streets.

Building developer Shane le Compte said he suspected the tagger was a Dunedin student and had sent evidence of the possible culprit's identity to police. The former office building is being redeveloped as a hotel with an opening date set for next year.

John Kirk-Anderson TOGO has become GO, as the cleaning effort reaches half way.

The TOGO tagger has also put his name on top of the nearby Rydges Hotel.

Le Compte said the tagger had dripped paint down the glass facade of the former Forsyth Barr building, leaving a big cleanup job for contractors. He said it would take time to clean all the paint from the building as it had to be done from a platform suspended from a crane, which could not be used in poor weather.

He did not know exactly how much it would cost to clear the paint, but said it was more than the $25,000 excess on his insurance policy.

John Kirk-Anderson The TOGO tag remains on the old Rydges Hotel.

"It is straight out vandalism," he said. "It is very costly. As they painted the tag they spilt paint all the way down the face of the building and on to the street."

He said it would have taken several hours to break through the four wooden hoardings and smash through the locked plant room doors to gain access to the roof.

"He certainly wanted to get his name up there," he said.

Street art expert Reuben Woods, who is completing a doctorate on graffiti in post-quake Christchurch, said taggers were drawn to high-profile spots as a way of gaining infamy.

"There is a daring aspect to it that allows a writer to gain fame or infamy. They want to find a spot that captures a public audience and impresses their peers," he said.

He said the trend of painting a tag in a high profile spot was influenced by marketing, billboards and naming rights for prominent buildings.

"I always compare pieces like that to the branding of a building. It is the same as a brand. We are complicit in suggesting that having your name big and bright in a prominent space is a sign of success."