Leicestershire County Council wants to close part of Snibston Discovery Museum to save £9.4m over 25 years.
But consultant Graham Black said the county council was "manipulating" the public by not revealing enough details about the impact of closing the centre.
A council statement said it cannot continue to subsidise the museum.
Mr Black, who has experience advising museums across the UK and lives in Leicestershire, said the attraction would bring £80m to the local economy over the same 25-year period.
"This is an exercise in trying to look as if you are giving choices but is actually manipulating people to agree with your point of view," Mr Black said.
He said the council had a responsibility to "store, care and maintain" the collection, which is located in Coalville, and includes a major quarry extractor, a bus, two aeroplanes, carts and horses.
The cost of removing and storing the materials would cost more than the money saved in closing it, he said.
The county council statement said the authority "needs to save over £110m and cannot afford to keep subsidising Snibston by more than £800,000 per year".
Mr Black suggested forming a charitable trust and applying for a £10m grant from the Heritage Lottery Fund to save the museum.
The chairman of the Friends of Snibston group Brian Voller said he was "increasingly concerned about the consultation process" and was planning to ask county council leader Nick Ruston to scrap the consultation, which ends on 7 July.
Councillor Rushton said earlier the Conservative-led council had "run out of time" and the only realistic alternative to scaling back the attraction was "complete closure".
A consultation on plans to scale back a Leicestershire museum has been criticised as misleading by an independent museum expert.