Departing ACT Brumbies star Matt Toomua has vowed to "show how much the club means to me" in his farewell season after signing a three-year deal with English club Leicester.

Fairfax Media can reveal Toomua will join Leicester at the end of 2016 after exercising a get-out option for the final year of his Brumbies contract.

Toomua made the agonising decision to leave Australian rugby at the end of the Super Rugby campaign after Leicester tabled a massive deal, ending his 10-year association with the Brumbies and his immediate Wallabies ambitions.

Reports from France on the weekend linked the playmaker to a deal with the Wasps despite having a Brumbies contract until the end of 2017.

However, Toomua signed with Leicester, with the chance to test himself in a new competition and family reasons being his motivating factors.

Toomua also had to consider his fiancee, dual international Ellyse Perry and her sporting career as she continues to star in the W-League soccer competition and for Australia in cricket.

News of his defection is a major blow to the Brumbies three months before the start of the Super Rugby season, but the club will groom teenage sensation Nick Jooste as his replacement while it is hoped Christian Lealiifano will extend his ACT deal.

Toomua wants to leave Canberra on a high and chase a drought-breaking Super Rugby title under long-time mentor Stephen Larkham.

"As a motivating factor, just ask any of the guys who have left, [knowing it's your last season] drives you a little bit more," Toomua said.

"I don't want to make bold statements or anything like that. I just want my actions to show how much the club means to me and for that I'll do all I can.

"Without selling it like a Hollywood trailer, I will do everything I can on the pitch. It's been very tough, a lot of very hard conversations with a lot people and myself. I don't take it lightly - after this year it will be 10 years with the Brumbies. That's almost half my life, they mean a lot to me."

The decision follows close mate Nic White's move to France earlier this year and Toomua is just 25 years old with a long international career at his feet.

In the past, overseas clubs have successfully poached established and veteran Australian players nearing the end of their careers.

But Toomua and White's departures indicate Europe is a viable option for young stars and is no longer viewed as a retirement village.

It will set off alarm bells at Australian rugby headquarters, with several stars off contract at the end of next year and openside flanker David Pocock already linked to a move to France.

Toomua has spoken with Brumbies coach Larkham and Wallabies coach Michael Cheika about his decision to leave Australian rugby.

It's understood Toomua was offered the option of starting a flexible contract with the ARU which would have allowed him to take a sabbatical overseas, but he decided on a clean break and a fresh start in England.

Cheika opted to use Bernard Foley, Matt Giteau and Kurtley Beale as Australia's chief playmakers at the World Cup while Toomua saw limited game time on the bench.

Toomua's deal with Leicester will keep him in England until 2019 and the length of the deal could open the door for him to return to Australia in time to be eligible for selection in the next World Cup squad.

However, Toomua said future World Cup prospects were not a factor in his decision.

"I felt it was the smartest thing for me to do and I'm pretty comfortable and excited about it. It's not easy to give up a potential Wallabies jersey, provided I was picked," Toomua said.

"I haven't looked that far ahead [to the 2019 World Cup], I'm committing to a club for a period of time and I want to do the best there without feeling I have one foot left at home."

The majority of the Brumbies squad will return to Canberra this week for the start of pre-season training with Wallabies players to return on January 4.