The province's new police training college, to be built on a 109ha site near Cookstown, Co Tyrone, will now cost £134 million, not the £80 million predicted last year.
These cost changes have come even before the team behind the project have appointed an architect to work up the proposals.
The project will contain 300 accommodation rooms, a specially built village for public order training and a decontamination unit to prepare for biological or chemical attack.
Defending the price hike, deputy chief constable Paul Leighton said the original bill did not include the cost of buying the land and fees for architectural work and wildlife, archaeological and heritage surveys.
'The cost in the last quarter of 2006, when the tender is to be let out, is around £134 million,' he said. 'It's not a major rise when you take building inflation into account.
And Barry Gilligan, a property developer and policing board representative on the college project, also insisted the actual costs have only risen by just 8 per cent after adjustments for oversights.
He said: `The product has changed so dramatically that, in my opinion and the unanimous opinion of the policing board, we are getting a significantly better product for the additional costs.'