Mr Johnston believes WA is being set up for disappointment much like an heiress who discovers she has spent - rather than saved - her inheritance.

"Sadly, the Future Fund will never exist. It is a dishonest con job. It shows a Govt [sic] fixated on spin rather than substance," Mr Johnston tweeted to WAtoday.com.au, following treasurer Christian Porter's announcement that the $1 billion future fund reflected a mining boom "that's not going to last forever."

Mr Johnston told WAtoday.com.au the fund was unrealistic "because it's in the public bank account."

"Colin Barnett is making out as if there will be a fund with money in it – there won't be. It's impossible for there ever to be a fund because of the way it's structured," Mr Johnston said.

"What you'll have to do is borrow money to put into the account. They're not allocating this money – it's just reallocating debt.

"In four years' time, there will be no money in the account, in 20 years' time there will still be no money in the account.

"If they actually had a future fund like they have in Norway, what they do is have the account and the money goes into that account and the budget operates separately.

"So in 20 years' time, instead they'll have no money in the bank account and $20 million of borrowing."

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