Sydney-based consultant Justin Barrett, director of Kazbar Projects, also accuses the ACT public service of trying to influence consultant KPMG in the preparation of a business case for the hospital, and of rewriting his emails of complaint.

KPMG has prepared a business case for the main tower and adjacent building at the Canberra Hospital, but it has not been released, and Health Minister Simon Corbell said on Friday it was "considered incomplete and insufficient".

Mr Barrett provided project director services for health infrastructure, including the hospital's expanded emergency department and the secure mental health unit, from January 2014. His contract ended at the end of June 2015 after a series of aborted tenders and he has now written to Chief Minister Andrew Barr with his concerns about the drawn-out and poorly handled tender process, and intervention in the business case, which he alleges was an attempt skew the outcome.

Mr Barrett's letter says he was invited in May 2014 to submit a tender for ongoing project director services. In August, the tender was cancelled.

He was asked to submit again, this time to be on a panel of companies to be used for territory work. At the end of February, he was told he had missed out. Despite the appointment of a panel of 15 firms, Mr Barrett was again asked in March this year to submit a proposal to continue as project director, but was told to reduce his rates. He sent the proposal in May, but was then told the job would go to tender.

Again, he was invited to submit, but wary of going into a fourth round without some certainty, so he wrote requesting confirmation that the government was committed to awarding the tender in June. The government responded that it was committed, subject, as always, to value for money and reserving the right to withdraw. Mr Barrett submitted a tender by the May 26 closing date, but was advised on June 2 that the tender had been cancelled because none had represented value for money.

Four days later, yet another request to tender for project director was issued, closing June 23, this time with a cap of $250,000. Again, Mr Barrett prepared a submission, but this time was unable to lodge the tender because, at the last minute, a public servant who was to join his team withdrew after being spoken to by a manager.

He believes the repeat tenders were an attempt to drive down costs.

"To have prepared four separate submissions purely for the convenience of the territory, and to service a wider agenda that was being pursued by the territory, represents highly inappropriate conduct for any entity in our opinion, not least of all for a government," Mr Barrett wrote to Mr Barr.

Mr Barrett also accused Treasury of involving itself improperly in the business case. Early this year, he was asked by ACT Health to manage the preparation of the business case, to be done by consultant KPMG. But he said Treasury contacted KPMG directly, telling the firm "a particular procurement methodology was required for the project and that the consultant was to ensure that the business case reflected this". The government wants a public-private partnership.

Mr Barrett complained to senior health bureaucrats about the intervention, saying the contact with KPMG could be interpreted as intimidating or even threatening and placed KPMG in a position of potential conflict of interest. The process should be terminated and a new one begun, he told the health department in February.

His letter to Mr Barr says the department asked him to withdraw his email, which he refused to do. Instead, he provided a clarification, which the department then amended. The amended version omits a reference to Treasury contacting KPMG about the affair.

As well as writing to Mr Barr, Mr Barrett has sent a copy of his letter and the email trail to Liberal leader Jeremy Hanson, and has complained to the ACT Ombudsman.

A spokesperson for the Chief Minister's Directorate said Mr Barrett's complaint was being actively considered.

Mr Corbell said more work was needed before a decision to redevelop the hospital buildings, and a taskforce had been established. No decision had been made on a public-private partnership, but value for money was the overarching priority when deciding how a project should be delivered, he said.