Mr Shorten and Victoria Police both say the investigation has been finalised and no criminal charges will be laid.

Mr Shorten said an allegation was made against him on social media when he was elected opposition leader last year concerning an incident in the 1980s when he was 19.

‘‘I will not go into the details except to say that the allegation was untrue and abhorrent,’’ he told reporters in Melbourne on Thursday.

The allegation was made by someone he knew briefly at that time.Mr Shorten said he had been thoroughly and vigorously investigated by police and he fully cooperated to clear his name.He freely answered all questions.

‘‘The easy option would be to say nothing but that is not who I am,’’ he said.

Mr Shorten said it had been deeply distressing and he was thankful for the love and support of his wife Chloe and backing of staff and colleagues.

‘‘It is over. I have no intention of making any further comment,’’ he said.

Victoria Police confirmed the allegation had been investigated and the advice from prosecutors was that there was no reasonable prospect of conviction.

‘‘All parties have been notified that Victoria Police will not be proceeding with criminal charges,’’ police said in a statement.