The convention centre site has been cleared and is ready for construction work to begin.

The amount spent on professional fees for the Christchurch convention centre is "eye-watering" but the details released by authorities raise more questions than they answer, a property development professional says.

Greater Christchurch Regeneration Minister Nicky Wagner last month revealed $34 million had been spent on "professional services", out of the central city project's total budget of $475m.

A breakdown of those professional service fees, released by Ōtākaro Limited under the Official Information Act, added up to $32.7m.

Supplied An artist's impression of the planned Christchurch convention centre.

The biggest expense was design consultancy at $11.4m.

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Other large expenses included $8.9m for commercial/project management advisers, $4.9m for legal advice and $3.8m for engineering consultants.

A property development consultant, who did not want to be named, said the fees were "pretty eye-watering", but he was not surprised by how high they were.

He said they probably included "preliminary costs that are pretty grunty because you're dealing with a clunky public sector".

Public sector projects were not comparable to private sector developments, but were generally less efficient.

The consultant said it was impossible to analyse the figures and pass judgement without a full project budget, and he did not understand why Ōtākaro had released just part of the picture.

"This just raises questions, in my view."

At an election debate earlier this month, Wagner said she would consider releasing the full project business case, but had not yet done so.

Rebuild critic and former Christchurch mayor Garry Moore, who requested the document, said he was "increasingly nervous" about the costs.

"To me the whole proposed convention centre as promised by the government was nuts."

He said the operating costs for the future owner, which he said might be the Christchurch City Council, would be "enormous".

"A future government is going to say 'Christchurch, this is yours, you pay for it' – and the ratepayers of Christchurch will have a huge albatross," Moore said.

"I want to know how they arrived at their numbers and I want to have them checked out by people who know what they're talking about."

The site had been cleared for construction and work on the centre was expected to be completed by early 2020.

CENTRE PROFESSIONAL FEES TO DATE

Design consultants: $11,439,627

Commercial/project management advisors: $8,859,176

Legal advice: $4,851,849

Engineering consultants: $3,809,425

Quantity surveyors: $1,497,233

Business and operational advice: $988,507

Quality assurance: $637,115

General consulting advisors: $456,295

Cultural advice: $85,583

Consenting/planning: $33,999

Insurance: $581