A 2011 ACT Civil and Administrative Tribunal ruling banned the YMCA from using the building as office space after residents and sailors fought the group's planned move into the venue, fearing it would strip the sailing club of space.

The Environment and Sustainable Development Directorate is investigating the complaint.

A directorate spokeswoman could not comment on the specific details of possible breaches to the Building Act 2004 and the Planning and Development Act 2007, nor the government's intended course of action.

"In accord with various laws that apply to investigations, ESDD cannot disclose evidence or opinion until a formal decision has been made and any affected parties have been given their right to be heard on any allegations," the spokeswoman said.

"ESDD has previously enforced the lease on block 1, section 18 Yarralumla as set out in the case of Young Men's Christian Association v ACT Planning and Land Authority and Others [2011] ACAT 78."

YMCA chief executive Jenny McCombe said she was unable to comment on the investigation.

She said the current focus was on expanding the activities at the sailing clubhouse.

A development application for a lease variation was approved about 18 months ago, she said.

"The focus is developing an aquatic recreation facility and expanding activities around that," she said.

"Hopefully we can engage more people in activities other than just sailing."

Ms McCombe said the YMCA was in the process of filling a new full-time position aimed at driving the development of aquatic recreation at the site and increasing numbers.

Similar past positions had only been contracted for the warmer months.

The new position would use the winter period to get plans for the follow season under way earlier.