New figures show the HSE spent €11.5 million less on dental care for medical card patients in 2011 than it had promised at the beginning of the year.

This 'hidden cutback' was in addition to the official cut in the allocation to the scheme in 2011, according to the Irish Dental Union.

The Union says the underspend is an 'outrage' as the scheme was already suffering from a chronic funding shortage. It has called on Health Minister James Reilly to launch an immediate investigation.

The HSE spent €51.5m on the scheme last year, which was €11.5 million less than the €63 million the Government had originally promised to spend on the scheme.

The Chief Executive of the Irish Dental Union, Fintan Hourihan, said the decision to cut funding from a medical card dental scheme that was already seriously underfunded was totally unacceptable.

Major spending cuts have been imposed on the medical card dental scheme over the past two years.

In 2010, the Government and HSE withdrew free routine care for medical card holders attending private dentists, restricting most cover to emergency care only.

The HSE 's 2012 service plan states that €63 milliion will be spent on the dental scheme this year.

"To withhold spending after providing a totally inadequate budget over the past two years cannot be justified. Last year, the number of medical card holders increased by 63,000 but instead of increasing spending, the HSE decided to underspend by €11.5 million", Mr Hourihan said.

"This means that the HSE spent €28 million less on the scheme in 2011 than it did in 2010. To cut a scheme which is already on its knees is a scandal and the Minister for Health has to explain how this occurred."

The Dental Union says it has also come to light that only one-in-four people who are entitled to a free oral exam attended their dentist last year.

According to the HSE data, 1.3 million medical card holders are entitled to a free oral exam every year, but only 325,000 people availed of this benefit in 2011.

The HSE figures show that overall, 450,000 fewer dental treatments were performed under the medical card scheme during 2011.