The company awarded the $1.3 billion contract to provide medical services to Defence Force personnel is having trouble signing up enough health professionals in the key defence cities of Townsville, Darwin and Canberra.
Medibank Health Solutions (MHS) won the lucrative four-year contract last year, but has angered doctors and specialists by cutting payments to below the rates recommended by the Australian Medical Association (AMA).
The AMA says the decision has meant many health professionals have not signed up to be part of the company's preferred provider network.
"Because of the poor uptake, Medibank Health Solutions has been forced to use non-contracted specialists to treat many patients," AMA president Steve Hambleton said.
Dr Hambleton says because of the shortage of signed-up health workers, some Defence Force patients have been given generic referrals for further treatment while MHS tries to find an appropriate specialist.
"We're not very happy with that model of care because that can lead to a situation where Defence personnel can be referred to the wrong specialty or discipline," he said.
RSL national president Ken Doolan says he has been made aware of concerns with the new arrangements and plans to raise them directly with Defence Force officials in coming weeks.
"Included in the membership of the RSL are many thousands of members of the Australian Defence Force, and some of those members have provided us with anecdotal information - and sometimes detailed information - about perceived shortcomings with the new arrangements," Mr Doolan told ABC News Online.
"We are gathering this information together, and when we have analysed it I will be seeking a meeting with the Defence leadership to discuss these issues."
The ABC has been told that some on-base medical officers have concerns about the operation of the MHS contract.
Medibank Health Solutions says as of December 14, it had signed up 3,503 medical specialists, 6,884 allied health specialists, 202 hospitals and in excess of 2,000 additional clinicians had joined since then.
The company's national medical director, Dr Ian Boyd, concedes there have been "challenges" in recruiting specialists in some regions, but the lower sign-up rate reflects a general shortage of medical professionals in some areas.
"Yes, there's challenges in some geographical areas recruiting and accessing medical staff, however... we're very confident that as this builds, we will be able to continue delivering the timely, high-quality, cost-effective care that Defence has had in the past," he said.
"Canberra, Darwin, Townsville are certainly areas that we are continuing to actively recruit, we're talking to health professionals in those areas and others."
As part of the contract with the Defence Force, MHS is responsible for providing health care to about 80,000 personnel.
Dr Boyd says despite the challenges in recruiting staff, there has been no degradation in the quality or timeliness of services.
"We are successfully delivering a quality service now [and] we've had very positive feedback from individual military personnel," he said.
"There's absolutely no delay in treatment. The quality, the timeliness of the services that were being delivered has been maintained right across Australia."
Asked whether the Defence Department had any concerns about how the contract was being operated, the ADF said in a statement:
"There has been no change in members' entitlements to health care. Full service delivery continues, providing high-quality health care to ADF members."
The Defence Force says it would not be appropriate to comment on the fees being paid to medical professionals, saying it is a "commercial matter" between MHS and individual specialists.
Last year, the Australian Society of Anaesthetists (ASA) wrote to the Chief of the Defence Force raising their concerns about the change in fee structure, warning "large numbers" of specialists would not sign up to the new arrangements.
He says there will be an impact on medical services for Defence personnel.
"It's certainly going to make accessing health care in the private sector problematic and that's particularly in the areas where there's a lot of Defence personnel... Townsville, Darwin and Canberra," Dr Grutzner told ABC News Online.
"What that means for Defence personnel in those areas, rather than having timely treatment and getting back to being fit for deployment, they'll be waiting potentially in the public hospital queue along with everyone else."
He says medical specialists have been paid at the AMA schedule of fees for about 40 years and is urging the MHS to give ground on the issue.
"Without any consultation with any medical bodies, they (MHS) unilaterally reduced the remuneration for anaesthesia in the order of about 27 per cent, and for other specialties it's even greater," he said.
But Dr Boyd has defended the fee changes, saying the new amounts are reasonable.
"The fees that we're paying we think are fair in the market place, and... we already have over 12,000 clinical staff who have signed up to that fee schedule and that contract who obviously also believe that to be the case."