UPDATED 5.37PM Justice Minister Amy Adams is rubbishing claims of a $5 million blowout to restore the Dunedin Courthouse.

Work on the building is set to get underway early next month, with South Island company Amalgamated Builders given the contract.

It will see the building strengthened to 60-70 percent of new building standard, as well as kitted out with improved security and IT features.

Initial estimates from the minister last September put the strengthening work at around $15 million.

But today, Ms Adams said $20 million has been put aside for the project.

"This is the scope I always anticipated it would be. I was obviously a little cagey with my numbers while we were negotiating and just said north of 15 million, which was always the case."

Work on the courthouse is set to finish at the end of next year, with full court services returning in early 2018.

WATCH ABOVE: Newstalk ZB reporter Matiu Workman has more on this story.