Mr Stewart, Canberra head of Elton Consulting, is working on the casino bid, as well as the Manuka Oval development. He was deputy chief executive in the government's Land Development Agency until August last year.

Greens Minister Shane Rattenbury refused a meeting with Mr Stewart about the Aquis bid to redevelop the casino, telling Mr Stewart he must first join the ACT's lobbyist register.

But Liberal Brendan Smyth was met Mr Stewart in September, before the casino bid was announced, to be briefed on the project. Mr Smyth said he had assumed that Mr Stewart, "having recently come from the ACT government, would be compliant with whatever he needed to be be compliant with".

Mr Smyth said he now believed Mr Stewart should be registered as a lobbyist "for clarity's sake", but the case highlighted how difficult it was to define "lobbying".

Planning Minister Mick Gentleman also met Mr Stewart on February 5 this year to discuss the casino bid. Elton's role was as "technical planning, consulting and architecture advisers", a spokeswoman said.

Mr Barr had formally met with Mr Stewart once since he joined Elton, in September to discuss the development of the city centre, a spokesman said. Senior public servants had also been at the meeting.

Lobbyist rules require anyone who communicates with a politician, a staffer or a public servant on behalf of a third party to be registered. Lobbying is defined as any communication with a public official to influence policies, decisions or legislation.

Mr Stewart said this week he did not intend to register as a lobbyist because his work did not amount to lobbying.

But Mr Rattenbury said his office always checked before agreeing to meetings.

"Dan Stewart did ask to meet with our office late last year [for a meeting this year] so we pointed him towards the lobbyist register guidelines. As he did not register as a lobbyist, we have not met with him in regard to any development proposals," a spokeswoman said.

The lobbying code of conduct also bans any former senior public servant - employed at head-of-service, director-general or executive level - from lobbying on any matter with which they had official dealings in their last 12 months.

The Land Development Agency was involved with the failed Telopea Park school land deal at Manuka Oval and the purchase of a Glebe Park site in early September, but the redevelopment proposals came as unsolicited bids and Mr Stewart said he never had any involvement with unsolicited bids, which were dealt with by Invest Canberra.

Questions about his involvement misunderstood his role with government, which had not been related to Invest Canberra. He didn't understand how anyone could imagine he might have inside information on an unsolicited bid, he said. Nor was he involved in the Manuka Oval masterplan.

On the "Manuka Green" bid, his job was community consultation, not government relations.

Mr Stewart would not discuss his work for the casino, but asked about his attempt to secure a meeting with Mr Rattenbury, he said he had made contact on behalf of a client - whom he would not name - who was overseas. His role was planning adviser, not lobbyist, he said.

"If I'm engaged as consultant with particular expertise and asked by a client to attend a meeting, then if I'm there to provide advice in relation to a particular area I don't believe that makes me a lobbyist," he said. "... I have no intention of acting as a lobbyist."

Mr Rattenbury's spokeswoman said Mr Stewart had been making representations on behalf of another company, and in their view a consultant acting on behalf of a third party fitted exactly into the lobbyist definition.

Both Liberal parliamentarians and Mr Barr were briefed ahead of the $800 million Manuka Oval redevelopment bid, but both said Mr Stewart had not been present at those meetings.

The Land Development Agency denied meeting Mr Stewart about Manuka when asked on Monday, but wouldn't answer the same question in relation to the casino.

Asked about any casino-related meetings with Mr Stewart, economic development director-general David Dawes said, "The Land Development Agency has contact with many individuals and businesses who engage consultants to assist them with planning, engineering, community engagement and other work. It is normal business for the LDA to meet with such consultants who from time to time include Elton Consulting ... Similarly CMTEDD officers from time to time meet with consultants."

Elton managing director in Sydney Brian Elton said the firm had undertaken thousands of projects for government and non-government clients and had always done it "with integrity and in a professional and ethical manner".