A blow for regional health services in South Australia's southeast.

A radiation therapy facility in Mount Gambier has been rejected for state government funding, a blow for regional cancer patients across southeast South Australia.

The southeast is the state's second biggest population with 60,000 people.

Shadow Minister for Regional Health Penny Pratt said, “sadly, about 200 people a year are diagnosed with cancer that requires radiation treatment.”

“Now they've got two options, they can travel to the city, country drivers know that's a five-hour one-way trip and the other option is to cross the border and access the Victorian service in Warrnambool,” she said.

Last year residents of the southeast and the Limestone Coast formed

a working committee, passing a motion for a petition which has garnered 16,000 physical signatories. The petition has been lodged in Parliament last week.

Ms Pratt said, “[it’s] really a community begging the state government to have another look at how this service can be funded.”

“It's a really important one and we're hearing people from Bordertown and Kingston, other places that would access that and find it easy to get to,” she said.

Rural people travelling for medical services will also have more out of pocket expenses.

“There is a lot of out-of-pocket costs, the accommodation and the range of other things that country people would have to undertake when they come up to Adelaide,” she said.