Carroll says "sport has been going backwards" and a $50 million cash injection in the lead up to the 2020 Olympic and Paralympic Games announced on Wednesday morning "still doesn't bring us back to where we started".

Government funding of high-performance sport has declined by 12 per cent in real terms since 2010 during a time in which Australia's results on the world stage have stuttered.

It comes after more than 40 current and former Australian athletes signed an open letter warning "high performance will inevitably transform into mediocrity" if sports are starved of Australian government funding.

Australia claimed a record 58 medals and finished fourth overall at the Sydney Olympic Games in 2000 but the nation has slowly slid down the ranks and settled for 10th at the 2016 Games in Rio.

Carroll says Australia is in danger of seeing that downward spiral continue if funds are not consistently pumped into Olympic sports.

If the investment into sport isn't made, Carroll says "the only gold medal won will be the race to the most obese nation and social mediocrity. This is not hysteria, this is fact".

"I am saying to Australia, with the appropriate investment into Olympic sports, we can be a successful nation," Carroll said at the National Press Club on Wednesday.

"If investment continues to decline, then I have to say it will be very hard for us to win many medals at a Games. It’s just going to be tougher and tougher.

Carroll will also scrap medal predictions for the Tokyo Games after Ian Thorpe and Kyle Chalmers said tally goals put too much pressure on athletes.

He is adamant creating a culture of "everyone is a winner" is the last thing he wants to do, but he believes investment in Olympic sports will be more than a cash grab for sporting bodies, as outlined in the letter signed by Australia's past and present heroes.

"When our glorious record of achievement at the Olympic, Paralympic and Commonwealth Games is substituted for a pathetic funding version of the Hunger Games, you know it’s time to say enough," the letter, published in The Australian, said.

"... When our current generation of athletes and future Olympians and Paralympians are forced to crowd source for the funds to represent Australia ... you know that we have a funding model that is broken," the letter continued.

The letter dubbed sport "an investment in our national wellbeing" after an inter-generational report estimated obesity will cost Australia $88 billion in the next decade.

Australia has fallen outside the top 10 in the world in high performance funding, having been fourth in 2004, with the likes of Great Britain, Germany and Japan surging past the green and gold.

Federal Minister for Sport Bridget McKenzie has announced a $50 million boost in high performance sport, which Carroll welcomes as a substantial boost over a two-year period.

However Carroll has called on the government to pump a further $60 million into sport on a consistent basis, which he believes is "not a lot of money" in the scheme of the federal budget "of some $488 billion".

He believes the government will recoup the costs via "ongoing returns that one-off campaigns and initiatives can never achieve" in stopping obesity in Australia through athletes inspiring people to be active.

"An investment of $60 million is very important, and it has to be consistent. You can’t just say ‘here’s a chunk of money for this year’ and pretend it goes away," Carroll said.

"A talent pathway takes a decade to bring champions through, which then inspire people to be participants, which then gets people off the streets and into the parks. The benefit for health and wellbeing is enormous."