The Mayor of Cairns is being investigated over a friendly loan that helped save his political career.

Cr Bob Manning became Mayor of Cairns in 2012, a year before he borrowed $150,000 from a developer lobbyist that spared him from bankruptcy, which would have disqualified him from office.

The money was borrowed from Ranjit Singh, a lawyer who represents developers in some of Cairns's biggest building projects.

Mr Singh was once listed by The Cairns Post as one of “Far North Queensland's most influential people”, and told The Sydney Morning Herald in 2014 that “the key in business is if you know someone has a potential weakness, you exploit it”.

Media reports say the loan was interest-free, never formally documented and has not been repaid.

Court documents filed in a separate legal action in the Cairns District Court allegedly reveal that the loan is payable “on demand” from Mr Singh.

Additionally, the Mayor did not declare a conflict of interest when projects involving Mr Singh’s clients came before Cairns Regional Council, including a half-billion-dollar tower development, a $300 million golf course redevelopment and a beachfront housing estate from Cairns's largest residential builder.

Queensland’s Crime and Corruption Commission (CCC) has launched an investigation after the state’s local government watchdog referred the matter.

Independent Cairns Councillor Brett Olds found out about the loan terms from reporters this week.

“If what you're telling me is true, I'm going to be pissed because I'm an elected member of that council,” he said in response.

“This isn't like, you know; ‘Aw, this is a grey area’.

“If you're going to take money off someone, a developer, or anyone that has anything to do with even building a house or a bloody shed, you have a legal obligation to declare that [in a council meeting].

“If this happens in a community with 169,000 people, there's going to be a lot of pissed-off people.

“They're going to be looking and saying; ‘What about this development? What about this one?’”

Cr Manning took 18 months to declare the money from Mr Singh, listing it on his register of interest as a “business loan” of more than $10,000.

The corruption watchdog has been told that one client of Mr Singh's, the Singapore-owned Nova Developments, received “significant incentives” from council at the urging of the Mayor for its proposed eight-tower high-rise project.

Questions have also been asked about the Mayor’s vote to allow another client of Mr Singh's, Kenfrost, to have a controversial development assessed without public notification.

Cr Manning is also due to face Queensland’s Councillor Conduct Tribunal on several separate misconduct charges, involving multi-million-dollar council contracts and a political donor.

The Mayor allegedly failed 24 times to declare a conflict of interest in council decisions to award building contracts and preferred supplier status worth more than $20 million.

Most of the matters relate to times before a ban on developer donations in Queensland came into effect in 2017.