The HSE spent over €76,000 on taxis every day last year.
That is according to figures obtained by Newstalk under the Freedom of Information Act.
The data shows the executive spent €27.9 million on taxis across the organisation last year.
The HSE says in many cases taxis are being used to transfer patients between hospitals and, at times, for the transfer of patient charts and files between hospitals.
"I don't believe the HSE has done a value for money audit," claimed Sinn Fein's Health Spokesperson Louise O'Reilly.
"I don't believe it that represents good value for money to be using taxis in this way.
"I also don't believe that the HSE has an excuse for not investing in good quality ambulances and good quality personnel to staff those ambulances," she added
Update: Conor O'Leary from Purple House Cancer Support feels their service could help to reduce costs for patient transfers using a scheme they already have in place:
"Most cancer support centres like Purple House have a team of volunteer drivers and these are people that are trained in areas of informal counselling and cancer care," he outlined.
"They drive patients to and from their hospital treatment and they give their time free of charge.
"We currently provide this service through fundraising so, with some funding, we would be saying to the HSE 'we'll provide this service for you at a more cost-effective level.'"