In an historic shift of allegiances, the FSC and SI unions have committed their future to the Brumbies. The new rugby region will be known as the ACT and Southern NSW Rugby Union.

The move comes after the two southern unions held dual affiliation with NSW Country and ACT rugby unions for the past two years.

Far South Coast president Peter Ryan said his union was genuinely excited by the opportunity to be a part of Brumbies' rugby.

"Since the ACT assumed responsibility for the development of the game on the Far South Coast two years ago, we've really gone ahead," Ryan said.

"Next year we will have our first full-time development officer for the region. It's all good and we know that it's the best decision for us and the best decision for developing rugby on the South Coast.

"We have struggled for years to promote the game in this area. Initially, we expect to concentrate on our juniors and expanding our Friday night and school competitions.

"There has been a real hole regarding juniors and this has affected our senior competition."

Ryan said he expected more resources to be provided to help rugby union grow in the South Coast area, including administration support, referee support and coaching accreditation.

"The affiliation will also provide pathways for representative teams and elite players to play outside the region," he said.

"The clubs were all unanimous in support of this decision. NSW Country have been quite silent about the matter and all they have done is try to discredit the move.

"But they haven't actually sent any support our way, so this affiliation with the ACT is a win-win situation.

"The ACT have said this is one of the most untapped rugby union zones in NSW and they really want to make it work."

SIRU president Ian Mawson said the decision was in the best interests of rugby in southern NSW.

"Our council voted unanimously to make the move," Mawson said. "It makes sense for us to be affiliated with a union that is geographically closer to our region.

"ACT rugby has worked incredibly hard over the past two years to show us that they are committed to developing the game in the region. We felt it was time for us to take the step and nail our colours to the mast."

Brumbies' rugby chief executive Rob Clarke said the new arrangement would help rugby move ahead in the region.

"We now have responsibility for a significant territory and with that comes a great deal of responsibility," Clarke said.

"We're delighted that after two years of trialling a relationship with the Brumbies, the two unions have the confidence in us to make it permanent. We've always felt a strong association with the country and today confirms that association. They are now our people in every sense".

Speaking from England where he is on tour with the Wallabies, Brumbies' captain Stirling Mortlock said the Brumbies players were pleased to hear the news of their new region.

"I passed on the news at breakfast this morning and the Brumby boys were very pleased," Mortlock said.

"We love getting out into the region, meeting our supporters and developing the game. We have a strong affiliation with the country and the players are happy that these two unions are backing the Brumbies."