In response to a question from Opposition infrastructure spokesman Shane Broad in Question Time last Thursday regarding how much it had cost the government to produce its 30-Year Infrastructure Strategy, Mr Ferguson said: "I am unable to give you a dollar amount because there was no outside consultancy at all."

But it's now understood the government did actually engage two consultants, at a cost of about $93,000 to the public purse, to assist in putting together a consultation draft as part of the strategy.

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The consultants are believed to have provided the government with advice on demographic and population projections.

In a statement, Mr Ferguson said he had become aware the answer he gave in Parliament was "incorrect".

"I'm now advised that there was consultant work to support the 30-year strategy in its development phase, commissioned prior to my appointment as minister in this portfolio," he said.

"I wrongly believed the work was all done by our team at Infrastructure Tasmania.

"Mine was an honest mistake and I will, of course, correct the record at my next opportunity."

Tasmania's Code of Conduct for Ministers states: "Ministers must not mislead Parliament or the public in statements they make and are obliged to correct the Parliamentary or the public record in a manner that is appropriate to the circumstances as soon as possible after any incorrect statement is made".

In a Cabinet reshuffle in June, Mr Ferguson took on the infrastructure and state growth portfolios, relinquishing responsibility for health.

Dr Broad said any claim the minister wasn't aware of the use of consultants was "an admission he has no idea what's going on in his own department and he should be seriously embarrassed".

The Braddon Labor MHR described the infrastructure strategy as "a complete dud" with "no projects, no actions and no recommended time-frames for development".

"Now we know despite Michael Ferguson's flat denial in Parliament, the Liberals spent almost $100,000 of taxpayer money on outside consultants," he said.

The government has come under fire from the Opposition as recently as last week for making use of consultants at a cost to taxpayers.

A $115,000 contract was awarded to public relations firm Corporate Communications to undertake community consultation around the Northern Regional Prison.

Mr Ferguson is expected to officially correct the record in Parliament on October 29, when the House of Assembly next sits.