St Helens sign NRL star Ben Barba on a two-and-a-half year deal.

The 27-year-old Barba's release from his lucrative contract with French rugby union club Toulon sparked a flurry of interest from Super League clubs and Saints on Wednesday announced his prized capture on a two-and-a-half-year deal.

St Helens have taken advantage of the new marquee player rule which allows clubs to make a second player exempt from the usual provisions of the salary cap, although he is likely to have to serve a 12-match ban before he can make his Super League debut.

New Saints head coach Justin Holbrook, who shares the same manager as Barba and coached the player earlier in his career, said: "I've known Ben for some time and am confident that he will add a new dimension to the Saints and is a great capture for Super League.

"He is a multi-talented and world-class rugby league player.

"Everyone in the team will benefit from him joining us and are really looking forward to his arrival. The fans also have a lot to look forward to.

"Given Ben's abilities and reputation, his signing was extremely competitive and the club have done exceptionally well to secure him.

"It is not often that players of his calibre become available and the club has pulled out all the stops to fight off competition from both rugby codes around the world.

"I am also grateful for their support to me for my first signing as the new head coach."

Barba, who won the Dally M award as the NRL's outstanding player in 2012, was released by Cronulla in November after testing positive for cocaine, shortly after helping them win the NRL Grand Final.

He was also handed a 12-match ban which he sidestepped by switching codes and signing for Toulon.

Although the Rugby Football League has confirmed that the ban will apply in Super League, St Helens chief executive Mike Rush hinted earlier this week that he would explore the possibility of an appeal.

If that fails, Barba will miss the last nine matches of the regular season and the first three fixtures of the Super 8s.

Barba, who played for Canterbury and Brisbane before moving to Cronulla, scored 99 tries in 168 appearances in the NRL and played for the Indigenous All Stars in 2011.

Barba, who spoke to both St Helens and Warrington during the Magic Weekend in Newcastle, said: "I feel very privileged to be joining such a historic rugby league club as St Helens.

"I was able to meet up with some of the players and key people from the club at the Magic Weekend and know they are a great set of people. The fans also showed me just how passionate they are.

"I wanted to make an early decision so that I can get my family settled in England and kids enrolled at school.

"I have certainly enjoyed my time in France at Toulon but I am a rugby league player and St Helens, especially with Justin Holbrook as head coach, have made me very comfortable with the decision.

"I look forward to pulling the Saints' jersey on and playing besides my new team-mates as soon as possible."

The signing of Barba casts some doubt over the future of St Helens' England full-back Jonny Lomax, who is out of contract at the end of the season.