Former All Black Mils Muliaina says he's looking forward to moving on with his life, after a sexual assault charge in Wales was dropped due to a lack of evidence.

The 35-year-old was arrested in April, over an incident on a Cardiff nightclub dancefloor the previous month, where he was accused of touching a 19-year-old woman "on the bottom over her trousers".

The Cardiff Crown Court was told on Monday that there was not enough evidence to obtain a conviction, and the charge would be dropped.

Outside court, an emotional Muliaina said it had been "a pretty tough seven months" for his family.

"I always knew I hadn't done anything wrong. The way I was treated, I suppose I'm a bit aggrieved by it, but I can still hold my head up high and, as the judge said, there is no stain on my character at all, so I'm happy with that, and just looking forward to carrying on," he said.

When he heard the charge would be dropped, Muliaina says his first thoughts were for his son, Max, who turns seven later this month.

"He should never have been through what he's been through and it's been clearly unfair. However, I am looking forward to getting back home to New Zealand next week ... We'll put this behind us and move on with our life."

'OUTRAGEOUS' CHARGE

His lawyer, John Charles Rees, QC, said the prosecution's case was "outrageous".

"My client has said from the beginning, 'No I didn't touch her' - and if it did happen, it was a case of mistaken identity," he said.

Muliaina would apply for costs to cover his expenses for travelling to court, 3News reported.

READ MORE: * Muliaina pleads not guilty in sexual assault case * Despite charge, Muliaina cleared for selection

The alleged incident occurred in early March when Muliaina's team, Connacht, were in Cardiff to play against the Cardiff Blues.

A month later, the fullback was arrested when in Gloucester after another Connacht game, and spent a number of hours in custody after he was driven by police back to Cardiff, a journey of about 100 kilometres.

His arrest was filmed and broadcast on television around the world.

The officers in charge felt afterwards that they needed more time to investigate and Muliaina was released on bail.

Muliaina's New Zealand-based agent Simon Porter accused the police of "grandstanding" in the manner they apprehended Muliaina.

"Of course the police must investigate any allegation and no one is above the law. However, as a lawyer, I have found it difficult to reconcile the manner of his arrest with the presumption of innocence.

"It was simply unnecessary to drag him off a rugby pitch under intense global media scrutiny. Unfortunately, it was a demonstration of police grandstanding at its worst.

"Mils is an outstanding individual and his patience and willingness to cooperate with the Cardiff police over the last seven months is testament to this.

"I always knew this day would come. Throughout the ordeal Mils has always held his head high and maintained his dignity. Now hopefully Mils, his family, friends and supporters can move on."

New Zealand Rugby Players' Association CEO Rob Nichol was also critical of the police work in this investigation.

"We are pleased for Mils and his family that he has been fully vindicated and like most people reading this news, we question how this was handled by the Cardiff Police," Nicol said.

"The manner of his arrest, poor investigative process and nature of the charge resulted in unreasonable and unwarranted damage to his public reputation and caused extreme anguish and stress for Mils and those close to him.

"While Mils may have legal avenues open to him should he choose to go down that path, you would like to think that someone in authority within Cardiff Police will be looking at the conduct of the staff involved in this matter."

Over his career, he matured into one of the All Blacks' most popular players and was appointed captain for the opening tests of the 2009 season.

He became the second player to reach 100 All Black caps when he appeared in the Rugby World Cup quarterfinal in 2011.

The Samoan-born player's silky skills saw him win a Super Rugby title with the Blues in 2003, and play several stints with the Chiefs.

He also won a Commonwealth Games gold medal with the New Zealand sevens team in 2002.

Muliaina is married to wife Hayley.