The Powerhouse Museum in Ultimo. Credit:Louise Kennerley Mr Borsak said he had found expert evidence to the inquiry that the move could cost up to $1.5 billion compelling, and said he was frustrated by what he called the government's excessive secrecy. He likened the government's refusal to offer details of its cultural or business case for the move to its alleged secrecy over the WestConnex project and the failed bids to scrap greyhound racing and amalgamate local councils. Speaking ahead of Tuesday's hearing, the museum's founding director, Lindsay Sharp, a world-recognised expert in museum construction, told Fairfax Media he believed the decision to move the museum had been made in haste and secrecy, without full consultation with the community or appropriate experts, by a government that was ideologically driven to encourage inner-city development. The decision to move the Powerhouse was made by former premier Mike Baird. It is understood he believed the government could raise $200-$300 million by selling the existing site to pay for the project, but Dr Sharp says the government had no idea how much the construction of a new museum and the transfer of a collection of around 240,000 artifacts would cost. Dr Sharp, who has consulted on the construction of major museums around the world, says when you added the cost of building a new museum shell, display environments, parking, warehouses and extra capital expenditure for flood mitigation next to the river to the sunk cost of the existing purpose-built museum and inflation over the life the project, "you are not going to get much change out of $1.5 billion".

Premier Gladys Berejiklian announced a deal with Parramatta council hours before a planned public meeting. Credit:AAP "If I am wrong about this, prove me wrong. Show me your numbers. Why are they being so secretive about this? It is not like they are planning a nuclear power station," said Dr Sharp. When she became premier, Gladys Berejiklian appeared to be reconsidering the move and announced two public meetings to be held to discuss it. The first went ahead in Parramatta on July 26. But hours before the second was to be held at the Ultimo site, Ms Berejiklian announced a deal had been made with Parramatta council to buy a site on the Parramatta River to house the new museum. The Catalina Flying Boat at Powerhouse Museum. Mr Shoebridge said he believed the government had changed its mind and decided to stand by the move because its MPs were "spooked like a pack of wildebeests" by criticism of the government's dramatic backflip over council amalgamation. "That's all this decision was. It was an anti-backflip backflip."

A spokesman for the NSW Arts Minister Don Harwin said the business case was expected by the end of the year, at which time the final cost of the project would be known. But he said speculation that it could cost billions was "wildly inaccurate and wrong". Shooters and Fishers MP Robert Borsak is frustrated by "the government's excessive secrecy". Mr Borsak said he believed the decision should not have been made before the business case was finished and published. "I'm an accountant, that is how I would have done it," he said. He believed there was now dissension on the museum's board over the move. Another opponent of the plan, Kylie Winkworth, a museum consultant and former trustee of the Powerhouse Museum, said evidence already presented to the upper house inquiry had "prompted incredulity and consternation" in museum circles. "There is not a single person working on the project who has any experience in museum planning. Yet they're going to blow around $1.5 billion of public money, a once-in-a-century investment in cultural infrastructure overseen by people without any experience."

David Borger, the Western Sydney director of the Sydney Business Chamber challenged the $1.5 billion estimate. "The costings of relocation should be based on the work of quantity surveyors and not on the opinion of activists opposed to the move," he said. Dr Sharp said the experts the government had consulted did not understand how much more difficult it was to preserve and move museum artifacts than art gallery pieces. As an example he cited the vast Catalina flying boat hanging from the ceiling of one of the Powerhouse's halls, which was so large and heavy its weight had been designed to help keep the structure of the building up. Should the museum move, he said, the 98 per cent of the collection that is in storage adjoining the museum's current site would have to be unpacked, appraised, insured and repacked before being moved, a job that would take years and necessitate importing overseas technicians. Loading "We just don't have enough people in Australia who can do it anymore," he said.

He said the pride of the museum's collection, the famed Boulton and Watt steam engine, which was first installed in a London brewery in 1785 and which he described as the "Mona Lisa of steam engines" might not survive a move and was effectively uninsurable.