Former All Black Mils Muliaina has been charged with sexual assault.

In a statement sent to the New Zealand Herald overnight, South Wales Police confirmed they have charged the 34-year-old and he will appear in court next month.

"Mils Muliaina has been charged with sexual assault on a female aged 16 or over. He is scheduled to appear at Cardiff Magistrates Court on the 7th August 2015," the statement said.

Mils Muliaina confirms that he has been formally charged by the South Wales Police but denies any wrong doing and intends to plead not guilty.

The charge comes after Muliaina returned to Cardiff to re-appear before police on Wednesday (NZT).

The Rugby World Cup-winner and 100-cap All Black was arrested by police on the morning of April 4 (NZT), shortly after his Irish club team Connacht had lost 14-7 to Gloucester.

Inspector Andy Walbeoff, of South Wales Police, has said the alleged victim was a 19-year-old female, local to the Cardiff area. Walbeoff was unable to confirm where the alleged assault took place, as it could "compromise further witnesses".

The alleged incident occurred in the first week of March, on the same night Muliaina was on a night out with teammates in the Welsh capital of Cardiff.

The group were out following Connacht's controversial 18-17 loss to the Cardiff Blues at Cardiff Arms Park on March 6 with Muliaina and others leaving an ex-pat Kiwi bar for a nearby nightclub at 3am.

At the time of his arrest, Muliaina's manager, Simon Porter, said the former All Black great was "pretty upset" and "shocked" about the sexual assault allegations. Attempts to reach Porter for commment this morning have been unsuccessful.

The Samoan-born fullback joined the Connacht team last year, and had announced in April he would be leaving the Irish club for Italian side Zebre at the end of the season.

Muliaina is understood to have split from his wife, Hayley, who have a six-year-old son together.

In 2010, he spoke of the difficult time he and his wife went through when their son was two months old and underwent open-heart surgery to patch a small hole in his heart.

Muliaina made his All Blacks debut against England in 2003. He played 102 matches for the All Blacks and cracked 100 tests in his final outing, New Zealand's 2011 Rugby World Cup quarter-final win over Argentina at Eden Park.

Injury ruled him out of the rest of the tournament but he picked up a winner's medal after being part of World Cup exits in 2007 and 2011. He finished his test career with 170 points and 34 tries.

Muliaina also won a gold medal for the New Zealand sevens team at the 2002 Commonwealth Games and a Super Rugby title with the Blues in 2003.

After the World Cup Muliaina took a contract with Japanese club side the Docomo Red Hurricanes, based in Osaka, where he played three seasons before signing a deal with Connacht.