Williams retains Bottas, Massa for 2015 Formula 1 season

While Massa was already under contract, Bottas was only under option so a new deal had had to be put in place.

Following successful talks, first revealed by AUTOSPORT last week, the Grove-based outfit confirmed ahead of the Italian Grand Prix that its line-up was sorted.

Team principal Frank Williams said: "Felipe is a pleasure to work with and combines raw pace with a wealth of experience.

"We have known for many years that Valtteri is a very special talent and in the FW36 we have given him a car that is allowing him to demonstrate his skills.

"The team is having a much improved 2014 season and the skill of our drivers and their feedback to our engineers has proved crucial in this.

"This announcement gives us excellent stability for 2015, but of course we are very much focusing our attention on maximising the full potential of the FW36 in the remaining seven races of this season."

Massa joined Williams for 2014 following eight seasons at Ferrari, while Bottas has been involved with the team since being signed as a test driver prior to winning the 2011 GP3 title. He made his grand prix racing debut with the squad last year.

Bottas added: "I've been a member of the Williams team for five years now and we have developed together throughout that time which is a great feeling.

"The team has also made some very impressive gains this season and I'm confident that I'm at a team that is moving in the right direction and can continue to be competitive."