The former head of global miner Rio Tinto Sam Walsh "has no fear of the truth at all" and a clear conscience over the miner's dealings in west Africa which have sparked a corruption investigation.

Earlier this year, Mr Walsh had part of his retirement payout withheld by Rio as the company waits for the outcome of investigations into payments made to gain access to a potential project in Guinea. The payments are now under investigation by authorities in Britain, the United States and Australia.

Addressing the "elephant in the room" at the start of an address in Brisbane on Wednesday, Mr Walsh said that, not withstanding some innuendo otherwise, Rio "has not made any accusation against me personally, nor do I expect that there will be".

"I operated ethically and legally at all times during my 25 years at Rio," he said, also recalling that at the recent Rio annual general meeting in London, the miner's chairman said there had been no admission of bribery or corruption by the company.

"I am positive that truth will ultimately prevail and I have no fear of the truth at all, hence why I come here today, with my conscience clear."

The Rio investigation was sparked by a leaked email exchange that took place in 2011 between Rio's then chief executive Tom Albanese and his successor Sam Walsh (pictured), who was running Rio's iron ore division at the time.

Earlier, Rio had suspended two senior officials over allegations surrounding payments made to access the Simandou iron ore reserves in Guinea, which are now the subject of police investigations in the UK, the US and Australia.

Access to half of the Simandou iron ore deposit at the centre of the investigations had been taken away from Rio in 2008, which Mr Walsh inferred was due to an unwillingness to pay bribes.

"Rio actually lost half of the deposit, because we weren't willing to play any of these games," he said. "That's currently going through arbitration and now it's in the courts and we'll let others decide all of that. But time and time again we had deposits that either just sat there for years, waiting for a brown paper bag that wasn't going to appear or we had the deposits taken away from us."

Mr Walsh refused to go into detail about what happened, citing the ongoing arbitration, but said the FBI and other agencies discovered that "something nefarious had happened".

"It was actually extraordinary that half the deposit would suddenly be taken away from us and given to a company that hadn't mined an ounce of iron ore in their history," he said.

The former Rio boss said a $US10.5 million payment to consultant Francois de Combret at the centre of the investigations was payment for lobbying.

"It was for work that he did acting as a lobbyist, ... helping us to put a new state agreement into place," he said. "This is a document two inches thick and it was a couple of year's work."

Mr Walsh declined to guarantee that none of the $US10.5 million payment ended up as a bribe but said he did not think the French banker was "that sort of gentleman".

Mr De Combret's contract "specifically stated that this (Rio Tinto) code of conduct, which prohibits bribery, that that would be followed", Walsh said.

Alpha Conde, the African country's president and a school mate of de Combret, was "masterminding" the discussions and a man of "impeccable qualities", Mr Walsh said.

In an address on 'leadership' Mr Walsh said there were three key areas of focus: firstly, making the tough calls, secondly delivering value in everything you do and finally, seeking to adapt and thrive, via personal development and reinvention.

"Don't fall into the trap of thinking that answering emails all day or using 'WhatsApp' is adding real value," he said.

"Leadership is all about: leading by example, motivating, engaging, involving and communicating. Ensuring there is clear accountability and ability to make the tough calls early are other defining characteristics."

Walsh also recalled the intense financial pressure Rio was under when he took the reins at the start of 2013, which prompted him to take the company back to the basics.

"When you become a chief executive you have to very quickly decide whether it's time for an evolutionary or revolutionary re-focus. I definitely wanted to move with revolutionary speed, but at the same time the company didn't need a wholesale reinvention," he said. "It needed leadership."

This involved bringing back "the operating discipline we were recognised for. A reset, to play to our traditional strengths", he said.

Prior to joining Rio, Walsh had worked in the auto industry, which taught him that the customer "really is king", how to be truly competitive, how supply chains work, and the like.

"My advice is don't get distracted - decide early on whether an issue is strategic (that's for the CEO) or operational, in which case, not surprisingly, you delegate the issue to your experts in the field. That way accountability moves to where it belongs."

"We are all leaders in whatever we do in our lives, we just need to recognise the context and take charge," he said.

Mr Walsh was recently appointed to the board of global trader, Mitsui and Co.