During Bowel Cancer Awareness Month, the head organisation of Australia's second deadliest cancer calls for a national guarantee to address diagnosis delays.

The wait time for follow-up colonoscopies in bowel cancer detection has been labelled the "Achilles heel of the screening process", according to the head of Bowel Cancer Australia

The organisation is calling on federal, state and territory governments to commit to a national guarantee.

The Colonoscopy Wait-time and Performance Guarantee would ensure a maximum wait time of 120-days between the first healthcare presentation to a follow-up colonoscopy.

That wait-time will then correspond with medical guideline recommendations.

BCA's executive officer Julien Wiggins said it was a "major concern" four in ten people in the public system waited longer than 120-days.

"If you wait longer than the 114-day mark and have a positive test, chances are, if you have the colonoscopy and cancer is present, your prognosis will be worse," he said.

Bowel cancer is diagnosed through a number of steps.

Firstly, a faecal occult blood test detects blood in faeces and a positive test means the person may have cancer.

Further testing, like a colonoscopy, is needed to determine the nature of the condition.

If cancerous and caught early, there is a 98 per cent treatment rate.

Each year, 15,604 Australians are diagnosed with the disease.

As part of the guarantee, BCA wants colonoscopy wait time reports from public and private facilities to be published.

"So long as wait times are not published and available, we can't measure them, Mr Wiggins said.

"We have no idea where resources or funding needs to be allocating to reduce them."

The guarantee would also outline minimum quality standards, performance indicators and collect patient-reported information about their experience within a 30-day period.

South Australia has the second largest wait-time for colonoscopies in Australia of 184-days.

As part of the state government's election campaign, $5 million was committed to a Bowel Cancer Prevention Initiative.

It promised to eradicate wait times within 12 months of the election, regularly publish colonoscopy wait times and pursue the national 120-day target.

Within those 12 months of the election, the number of people overdue for a colonoscopy dropped from 4100 to 3600.

In March, the state government committed a further $45 million over two years to continue reducing that number.

The money allows hospitals to undertake additional procedures to reduce the backlog.

It also enables country and private hospitals to carry out procedures if necessary.

Health Minister Stephen Wade said the colonoscopy wait times were "unacceptable".

"The people of South Australia expect us to get these lists down further as we promised, and that's exactly what the state government is doing," Mr Wade said.

He said more than 1000 referrals were made to private providers and the list across all Local Health Networks reduced by 400 people last month.

"By June 20 we expect it to be significantly lower as more procedures are carried out by private providers."

As South Australia's ageing population increases, so does the demand for colonoscopies and eligible people to access the National Bowel Cancer Screening Program.

The program allows people aged 50-74 to test for bowel cancer using a free at-home kit.

SA's participation rate in the program is the largest in Australia at 47 per cent, according to the Australian Institute of Health and Welfare data.

The national average is 41 per cent.