Ducati signing Jorge Lorenzo says he needed a new MotoGP challenge

Lorenzo had previously insisted his preference was to spend his entire MotoGP career at Yamaha, with which he has won three titles since being signed from the 250cc series at the start of 2008.

But on Monday Ducati and Yamaha confirmed Lorenzo would be departing for the Italian team next season.

"As you all know next season I won't be with Yamaha," said Lorenzo.

"I felt I needed a change, a new challenge in my career, set new goals for me to try to achieve and keep my level of ambition at the maximum."

Lorenzo's 2015 title success came at the end of a fraught season in which team-mate and defeated championship rival Valentino Rossi intimated the Spaniard had received help from Honda's Marc Marquez, with whom Rossi was embroiled in a huge feud.

Yamaha offered both Rossi and Lorenzo new contracts ahead of the 2016 season, but while Rossi rapidly signed up for a further two years, Lorenzo held off and eventually decided to leave.

He insisted his relationship with Yamaha remained good and there would be no let-up in his efforts over his remaining races with the team.

"I have only words of gratitude to the Yamaha family because of all the moments we lived through together," said Lorenzo.

"I achieved much more than I'd ever dreamt.

"What will happen in the future is unpredictable but from here on I just want to enjoy these 15 races that I have left with Yamaha to try to ratify the world championship.

"This is right now my only target."

Suzuki rider Maverick Vinales is favourite to take the vacant Yamaha seat alongside Rossi next year.

Ducati is yet to decide which of its current riders Andrea Dovizioso and Andrea Iannone it will drop to make space for Lorenzo.