Mr Hargreaves claimed "a number of members of the [Labor] party" had "expressed outrage" at the cost of the appointment - which he believed would amount to more than $2 million over five years.

"Much of the concern has been that there have been requests for money out of the budget for good and valid purposes which have been knocked back on the basis that there haven't been any funds available to do this. But funds can be found to take out a political opponent. And that, for me and for the people who have spoken to me, is a matter of concern."

Mr Hargreaves's comments come after Chief Minister Andrew Barr appointed Mr Smyth, a key member of the Liberal team, to a new job as Commissioner for International Engagement.

Mr Smyth has said the pay package is worth about $300,000 a year for five years.

Mr Barr made the appointment last week, but it didn't go to Cabinet for approval until Tuesday this week.

The Greens' Shane Rattenbury is a member of Cabinet and has expressed reservations.

He said he had told Cabinet that he would have preferred a public call for expressions of interest for the job. "Given Mr Smyth's background and knowledge of the ACT, he may well have been successful anyway, but the EOI process would have provided greater transparency for the community," Mr Rattenbury said.

Mr Barr said Cabinet had unanimously endorsed the appointment.

The Canberra Business Chamber had expressed its confidence in the appointment, but other than "business and political insiders", there had been very little feedback. What had been received had been overwhelmingly positive, he said.

Mr Smyth had the right credentials with a detailed understanding of the ACT economy, government, business community, diplomatic community and federal government.

Mr Hargreaves is a political opponent of Mr Barr, the pair having fallen out over a preselection battle for the federal seat of Canberra in 2010 when the pair backed different candidates. Like Mr Barr, Mr Hargreaves was a member of the party's right faction, but has quit the faction.

Mr Hargreaves is now involved with the Victims of Crime Assistance League, which lost $200,000 in funding from the ACT government in 2012. The organisation lost the funding in 2012 when the contact was awarded instead in a tender process to Communities at Work.

"And yet the government can find $300,000 to pay for what is a very spurious activity," he said, dismissing the international engagement position as "at best superfluous".

Other urgent community needs also trumped the need for an international engagement commissioner, including more public housing.

Mr Hargreaves pointed to another issue with which he is concerned - the government's successful challenge to an $8 million compensation payout for Jonathan Crowley, shot by police in 2001 and now a quadriplegic.

"I would argue that Jon Crowley's needs should be met before Brendan Smyth's needs to exit stage left," he said.

Mr Hargreaves questioned why Mr Smyth was being paid at the top level of an ACT commissioner, and substantially more than he was receiving as a parliamentarian. Human rights commissioners took a pay cut in July to a basic salary of $188,600. The president of the Human Rights Commission is paid a base salary of $216,000.

"It is this sort of surprise that makes it very difficult for average rank and file members of the party to defend accusations of arrogance," Mr Hargreaves said, speaking as the Labor Party prepares for its annual conference on Saturday - expected to be a largely uncontroversial affair given the closeness of the election.

Mr Hargreaves, left the ACT parliament in 2012 after 14 years, including six working alongside Mr Barr. He represented Tuggeranong voters alongside Mr Smyth, the pair entering the Assembly at the same election, 1998, in the same seat, Mr Smyth for the Liberals and Mr Hargreaves for Labor.

Mr Smyth's departure puts a question mark over the Liberals' hopes to win at least three of the five Tuggeranong seats in October.