A complaint against a Sinn Fein MLA over a lewd joke about the birth of the royal baby is to be investigated by the Assembly Commissioner for Standards.
Douglas Bain confirmed he will probe the issue even though Phil Flanagan apologised and said he did not intend to cause offence.
Mr Bain told Traditional Unionist Voice leader Jim Allister, who brought the complaint, that he has started his investigation.
North Antrim MLA Mr Allister said while not surprising, the remark was unwarranted and a breach of the Code of Conduct that all MLAs are bound by.
The code states: "Members have a general duty to act in the interests of the community as a whole" and "Members will act in a way that is conducive to promoting good relations by providing a positive example for the wider community to follow..."
Mr Flanagan, who retweeted the joke to his 3,600 followers on the social network, explained: "In a split-second error of judgment, I misconstrued the meaning of this tweet and retweeted it to my followers in that context.
"I innocently believed that this joke was about an expectant father being spotted entering the hospital through the front door, leading to a two-day media circus with no news to report.
"In hindsight, I can now understand the potential double meaning that some may read into this, but this was not my intention."
The Fermanagh and South Tyrone MLA repeated the remark before the birth of Prince George Alexander Louis and had also joked on Twitter the previous day on the same topic. The earlier quip said: "I've got a library book that's like Kate and William's baby. It's overdue and I'll end up having to pay for it."