Jenson Button’s Formula 1 future remains in doubt after McLaren boss Ron Dennis revealed the team are keeping an eye on the availability of other leading drivers.

The 2009 world champion is in the final year of his contract at the Woking squad having joined the team in 2010.

Button’s future at McLaren has been shrouded in doubt in recent weeks with the team yet to hold contract talks with the 34-year-old, 15-time grand prix winner.

The Brit’s team-mate Kevin Magnussen, who made his F1 debut with the squad this season, is also yet to be offered a new deal for 2015.

The Dane has impressed the outfit with his recent performances, despite being outscored 68-37 in the points table by his more senior team-mate.

Speculation regarding the make up of the 2015 McLaren driver line up has been growing, with team boss Dennis adding fuel to the situation by confirming the team are monitoring the availability of other leading drivers.

Dennis is eager to arrest McLaren’s slide down the order having gone 31 races without victory.

While he declined to reveal names, Red Bull’s Sebastian Vettel and Ferrari’s Fernando Alonso have been linked to the team. The duo’s contracts at their respective teams are due to expire at the end of 2015 and 2016 respectively.

Dennis told the official Formula 1 website that while he is happy with drivers Button and Magnussen this season, he is still keeping his options open for next season, which will see Honda return as McLaren’s engine supplier.

“As I say, we’ll always look to employ the best drivers available – but they have to be available, don’t they?,” said Dennis.

“Having said that, for the avoidance of doubt, Jenson and Kevin represent an excellent blend of capable experience and youthful promise, and we’re very happy with both of them.

“The fact that we’re keeping an eye on what a few other drivers are up to in no way contradicts that, because, as I say, if opportunities arise, we’ll appraise them – we always have and we always will.”

Although desperate to continue his F1 career, Button admitted at the Belgian Grand Prix that he could be forced to retire from the sport if he losses his seat at McLaren.

“If I have to retire at the end of the season then so be it, but I feel I have so much more to give and I can’t imagine life without motorsport and especially Formula One,” he told the BBC.