The Labor lord mayoral candidate said it was time for incumbent lord mayor Graham Quirk to leave his office.

“This lord mayor thinks he’s untouchable,” he said.

“We need new blood in our councils.”

This is Mr Harding's second tilt for Brisbane's top job, at the 2016 election he secured 40.49 per cent of the two-party preferred vote, leaving Cr Quirk with 59.51 per cent.

Mr Harding, a father-of-three, told Fairfax Media he tried to not reflect on the 2016 loss and was starting from scratch for his 2020 campaign.

“It certainly wasn’t fun losing,” he said.

“We went and had a Chinese meal the Sunday after, there might have been a couple of tears from a few people in the family, but after a few days, you’ve got to pick yourself up and dust yourself off."

The Ashgrove resident remained active and very vocal on social media following his 2016 loss, often criticising the policies of the LNP.

“I think I’ve been a fairly vocal critic of the lord mayor, but completely justified in all of my criticism,” Mr Harding said.

He was quick to change his social media accounts to “Rod Harding for Lord Mayor” after he announced he would run in the 2020 election for mayor on Wednesday.

Mr Harding was uncontested in his nomination as Labor’s lord mayoral candidate.

“I look at it as I’m a massive underdog,” he said.

“Graham Quirk has an 18 point margin ... and that’s how he treats the people of Brisbane. Like he’s got an 18-point lead.”

“That’s not acceptable, that’s got to change.”

Mr Harding said his best credential for running for mayor was that he had never been elected to council but was a very good businessman.

“I know numbers, I know money and that’s really important when you’re talking about a multibillion-dollar budget,” he said.

The 49-year-old has degrees in law and business and a masters of applied finance.

He worked in North America for several years with Macquarie Bank before returning to Brisbane with his wife Anna, where he wanted to raise his three children, Jack, Alice and Lucy.

Mr Harding, who was schooled at Marist College Ashgrove, said he would continue to do some consulting work, but his main focus, on a daily basis, would be talking to residents and taking on Cr Quirk.

“My focus is initially taking the fight up to Graham Quirk and establishing what this election is going to be fought on,” he said.

“I really think [it] is going to be about a time for a change because of the culture of arrogance in this administration.”

Cr Quirk said he never underestimated any competitor.

“Mr Harding has been the only name that has been emerging in recent months, we will be focused though on doing the job we need to do for the people of Brisbane,” Cr Quirk said.

Deputy mayor Adrian Schrinner said if Mr Harding was serious about the people of Brisbane he needed to commit to supporting the council’s Brisbane Metro project.

In 2016 Mr Harding made several election commitments, including a $1.2 billion light-rail system, $20 million for an extra 120 suburban bus services and to fast-track the construction of a pedestrian bridge between Kangaroo Point and the CBD.

He said, despite the LNP’s Brisbane Metro project not being the “Paris-style subway” promised, Labor would not scrap the project if he was successful in 2020 but would complete the project “without fuss”.

It is unclear if the term “Rocket Rod”, as he was dubbed by the Labor party during the 2016 election, will return this campaign.

“My name is Rod Harding. My mother calls me Roderick,” Mr Harding said.

“The most important thing is people hear my message and when people judge me against the current lord mayor I hope they judge me favourably. From what I’m hearing, I think they will be.”

The next Brisbane City Council election would be held be on March 28, 2020.