Jenson Button has been confirmed as a McLaren driver for the 2015 season.

The future of the 2009 world champion had been in doubt for several months, with McLaren putting off a decision on whether Button or Danish team-mate Kevin Magnussen would drive alongside the returning Fernando Alonso.

But McLaren have now officially announced their line-up for next year, tweeting a picture of Button alongside Alonso ahead of a press conference at their Woking headquarters.

Button said on the team's website: "I am extremely excited to be embarking on my 16th year in Formula 1 and my sixth season for McLaren.

"Like Fernando, I am certain that McLaren and Honda will achieve great things together, and I feel sure that, working together, all of us will pull incredibly hard to create a brilliantly effective winning team."

Magnussen will remain with the team as test, reserve and third driver and Button, while thrilled to have got the nod, is glad the Dane is staying as well.

"I am very pleased to have been invited to do my bit. In fact, I am absolutely raring to go," he added. "I am also very glad that Kevin will remain part of the team. He is a very quick driver and a really nice guy."

Amid the excitement of the announcement Button also had a bit of fun on social media, tweeting: "Just woken up, what's going on?!"

McLaren group chief executive Ron Dennis, who has been criticised for the protracted nature of the team's selection process, is confident the wait was worth it and they have a duo to be reckoned with.

"McLaren's policy has always been to assemble the strongest line-up possible, and in Fernando and Jenson I firmly believe that is exactly what we have," he said.

"For many reasons our negotiations with Jenson took quite a long time, but, now that they have been concluded, we are confident that our collaboration with him will continue to thrive in the future every bit as well as it has in the past.

"Make no mistake about it, Jenson is 100 per cent committed to McLaren-Honda, to Formula 1, and to winning."

Group chief executive Dennis took a surprising amount of time over deciding whether to retain Button or Magnussen.

Dennis has faced criticism, in particular after stating at the Italian Grand Prix in September a decision would be made before the final race of the year in Abu Dhabi in November.

Mika Hakkinen, a former double world champion with McLaren, told Swiss newspaper Blick that "what is happening at McLaren is unworthy of such a team".

Yet Button will drive on for the team he joined in 2010, initially as a team-mate of fellow Briton Lewis Hamilton.

In his first five seasons with the team, he has finished fifth, second, fifth, ninth and eighth in the drivers' championship.

Since making his debut as a 20-year-old Button has amassed a total of 1,198 career points in F1, winning 15 grands prix.

He has started 266 races, which is the third highest in F1 history behind Rubens Barrichello and Michael Schumacher.

Alonso also brings significant pedigree to the new-look McLaren line-up for next year, having won two world championship titles, and 34-year-old Button believes they will make a great team.

"Last but far from least, I am very much looking forward to having a driver as fast and as experienced as Fernando as my team-mate. I am sure we will work extremely well together," he said.

The Spaniard, 33, joins McLaren from Ferrari and it will be the second time he has raced for the Woking-based team after a turbulent spell in 2007, but now he wants to remain for the long haul.

"I am joining this project with enormous enthusiasm and determination, knowing that it may require some time to achieve the results we are aiming for, which is no problem for me," he said.

"Over the past year I have received several offers, some of them really tempting, given the current performance of some of the teams that showed interest.

"But, more than a year ago, McLaren-Honda contacted me and asked me to take part, in a very active way, in the return of their partnership - a partnership that dominated the Formula 1 scene for so long."

Alonso revealed that the pull of following in the footsteps of Ayrton Senna, who won three titles during a glorious five-year spell with McLaren from 1988 to 1993, was too good to turn down.

He added: "I have never hidden my deep admiration for Ayrton Senna, my favourite driver, my idol on track, my reference.

"I still remember, as a kid, the posters in my wardrobe, my toy cars in which I dreamed I would one day emulate Ayrton."