Bottas tasked with pushing Hamilton as Finn is named as Rosberg's replacement

Bottas, the 27-year-old who is yet to win a race in Formula 1, will partner Hamilton for the forthcoming campaign after joining the world champions from Williams.

Fernando Alonso, the two-time world champion enduring an arduous spell at McLaren, and Ferrari’s Sebastian Vettel, a winner of four titles, had been mooted as mouth-watering candidates to join Hamilton at Mercedes after Rosberg’s shock decision to retire in December. But with both drivers under contract at their respective teams, and the prospect of another fierce inter-team rivalry, Bottas quickly emerged as Mercedes’ preferred option.

Bottas, who made his grand prix debut with Williams in 2013, is expected to play second fiddle to Hamilton. But Mercedes boss Toto Wolff insists his new driver will provide a stern test for Hamilton.

“They are very different and not in the same way that Nico and Lewis were,” said Wolff. “Lewis wears his heart on his sleeve and is a very passionate and emotional driver.

“Valtteri is at the other end. As a Finn he is almost shy, timid, and I think as a team you need to have the best of both worlds.

“Lewis is probably the best driver in the world at the moment and if he gets it together on a weekend he is, in my opinion, almost unbeatable, but Valtteri has all the ingredients.

“We haven’t seen him in a car that has been capable of challenging for championships, and that is a different step, but I certainly think Valtteri can give Lewis a run for his money.”

Bottas’ vacant seat at Williams will be filled by his former team-mate Felipe Massa, who emerges from a retirement which lasted just 49 days.

Bottas was highly rated by those at Williams, and his former employers have long touted him as a champion in the making.

He comfortably had the better of Massa during their three seasons together, but has never started from pole position, finished on the podium only nine times, and whether he has the ability to cope with Hamilton’s star quality on a regular basis is uncertain.

“Lewis is going to be a great reference,” Bottas said. “He is a world champion and everyone knows exactly how good he is.

“He obviously has more experience than me, but I see us as a good pair for the team and I am sure we can work well together, share a lot of things, and hopefully push each other forward. That is very good for the team.”

Meanwhile, Mercedes also announced that Rosberg, who walked away from the sport just five days after being crowned world champion, has accepted an ambassadorial role with the team.

His first duty will be to appear alongside his old rival Hamilton at a sponsors’ event in Switzerland on Tuesday.