Liberal MP Sam Duluk will attend Parliament when it resumes, despite an ongoing investigation into his conduct at a Christmas party last year.

Key points: The alleged incident occurred at a parliamentary Christmas party last year

The alleged incident occurred at a parliamentary Christmas party last year Liberal MP and Parliament Speaker Vincent Tarzia has launched an investigation

Liberal MP and Parliament Speaker Vincent Tarzia has launched an investigation SA's Opposition has called for Mr Duluk to be stood down

Mr Duluk has faced the media for the first time since he allegedly slapped SA Best MP Connie Bonaros on the behind, and acted inappropriately towards staffers at the December Parliament House event.

But while the embattled MP has apologised via social media for his behaviour, he declined to elaborate any further.

"As you know, there's an independent investigation at the moment, so not making any further comments but will certainly be in Parliament next week and will continue to serve my electorate of Waite," Mr Duluk said.

Parliament's Speaker, Vincent Tarzia, has launched an investigation into Mr Duluk's behaviour, which is headed by a private investigator.

Mr Duluk made the comments about his future outside a Liberal Party summit on Kangaroo Island, where MPs gathered to discuss the year ahead.

But Labor said he should not have been invited, and should instead be stood down from the party.

"Surely in any other workplace in Australia, he'd be out, he'd be fired, but instead, they are welcoming him with open arms," Labor frontbencher Tom Koutsantonis said.

"The people of integrity and honesty and honour are going to get up and walk out of that room until Sam Duluk leaves the Liberal Party."

Premier Steven Marshall defended Mr Duluk's attendance at the summit.

"I think I've been really clear the behaviour towards the end of last year was completely unacceptable in any workplace," Mr Marshall said.

"Now there's a process underway. It's not going to take a long period of time. We'll get some results really soon."

It is not clear whether the results of the investigation will be made public.