A Queensland Ombudsman report has revealed that 15 to 18 per cent of births to Indigenous mothers were not registered, compared with 1.8 per cent to non-Indigenous mothers.

Queensland Ombudsman Phil Clarke said there were significant lifelong restrictions to participating in society when a person's birth was not registered, and they did not receive a birth certificate.

"Without birth registration, a person is effectively 'legally invisible' and can suffer significant disadvantage as a result," he said.

"The disparity between rates of registration for Indigenous and non-Indigenous births raises concerns of an unintended, yet potentially discriminatory, effect inherent in Queensland's birth-registration process."

The report did not find any deliberate action that resulted in higher rates of Indigenous births not being registered.

The investigation found some people were denied school enrolment because they did not have a birth certificate, or had trouble getting a driver's licence, opening a bank account, getting a tax file number, or applying for housing.

The Ombudsman expressed concern over whether the under-registration of Indigenous births could affect the government's ability to accurately identify the need for schools and health services in some areas.

But Queensland Treasury officers said it would have minimal impact on funding, as the Australian Bureau of Statistics calculated population data based on a variety of sources.

Mr Clarke analysed Queensland Health data from 2014 and interviewed Registry of Births, Deaths and Marriages staff, and spoke to representatives from other agencies such as hospitals and Youth Justice to determine which practices needed to be changed.

His investigation found the current level of coordination between Queensland government agencies was inadequate, and there were no current targets to address the under-registration of births.

The report concluded that Births, Deaths and Marriages had taken inefficient action aimed at increasing or monitoring the rate of Indigenous birth registration, and found a shift towards online registration may have created barriers.

Departmental figures, however, showed 90 per cent of children born to Indigenous mothers were registered within five years of their birth.

The Ombudsman recommended the Department of Justice and Attorney-General director-general review fees; make clear the distinction between the free process of registering a birth and the process to obtain a birth certificate, which includes a cost; develop a fee-wavier policy and create a cross-agency strategy across government to improve the rate, in consultation with Indigenous communities.

Queensland has the second-largest Indigenous population in Australia, making up 4 per cent of the residents.

LNP Shadow Attorney-General David Janetzki called for the government to act.

"Labor need to focus on getting back to basics and make sure the birth of all Queenslanders are actually recorded," he said.

A spokesman for the Department of Justice and Attorney-General said the Registry of Births, Deaths and Marriages did not shy away from the important issue of increasing the rate of Indigenous birth registrations.

"[It] continues to work with partner agencies to improve these outcomes and close the gap against non-Indigenous rates," he said.

The spokesman said strategies included partnering with Pathfinders, which allowed more than 3000 certificates to be issued to Indigenous clients at no cost last year and 600 births to be registered.

A community engagement officer also visited remote Indigenous communities and programs were developed with sporting bodies such as the NRL to encourage birth registration.

The spokesman said a review of the Act was being conducted, and the director-general supported any recommendations that would increase birth registration.