Michael Cullen says he will be cleared of covering up the billion-dollar blowout at ACC and is taking heart from the fact that the now-completed ministerial inquiry did not speak to him.
Dr Cullen said the lack of contact showed that the inquiry - ordered by Prime Minister John Key - "hasn't proved what they wanted".
The absence of the blowout from the pre-election "opening of the books" saw National accusing Labour of deliberately trying to hide the sum to make the Government's books look better than they were.
The blowout took the incoming National Government by surprise and Mr Key ordered the inquiry to find out why the "significant and serious" hole was not included in the Pre-Election Economic and Fiscal Update - which Dr Cullen was responsible for as Minister of Finance.
In Parliament this month, Mr Key pointed to Dr Cullen's involvement, saying "maybe we should have concern for a former minister of finance who may well find himself in breach of the Public Finance Act".
The act requires the update and breaches are punishable with up to a year in prison or a fine of $5000.
Neither Dr Cullen nor former ACC Minister Maryan Street was spoken to by the inquiry, which was led by consultant Michael Mills. Its report is to be given to the Government today.
Dr Cullen said the inquiry was set up for "political reasons" and "did not even interview the two previous ministers who were at least in some respects supposedly in the firing line".
He had applied under the Official Information Act for advice he received on ACC while finance minister during the relevant time period.
"I've not been provided access to the material that might provide my own defence in the case of need."
The application was made to Treasury but the reply came back on the letterhead of the present Finance Minister, Bill English.
Dr Cullen said he found it extraordinary that he was declined access to three particular papers on the grounds that it was to protect the free and frank advice of public servants - "when the advice was to me".
He said he had complained to the Ombudsman.
Dr Cullen said he had wanted the information to jog his memory but now believed the inquiry was going nowhere and had moved to a lower level.
A spokesman for Mr English's office, which is responsible for the inquiry, said the minister would not comment until the report was released.
Dr Cullen will leave Parliament to become a treaty negotiator for central North Island tribe Ngati Tuwharetoa, TV3 reported last night.
It will mean switching sides of the negotiating table for Dr Cullen, who was previously Treaty Negotiations Minister.
Dr Cullen would not comment last night.
He is widely respected within Tuwharetoa after negotiating the signing of the "Treelords" deal last year.