File picture: Hamad I Mohammed / Reuters.

London - Formula One drivers, including Britain's four times world champion Lewis Hamilton, have shown rare unanimity by all signing up for their union amid concern for the sport's future direction.

Grand Prix Drivers' Association (GPDA) chairman Alex Wurz told the BBC on Wednesday that the Monaco-based organisation now had 100 percent membership "for maybe the first time in history".

Hamilton, who clinched his fourth title with Mercedes this year, has not been a member in recent seasons while others who had been outside the body had included Ferrari's 2007 champion Kimi Raikkonen.

Wurz said Formula One, whose ownership changed in January with US-based Liberty Media taking over, was entering "a period of evolution, change and perhaps even a degree of turmoil.

"They (the drivers) recognise they must be united and represented to face that challenge."

The contracts between teams and commercial rights holder mostly expire at the end of 2020, as does agreement on what kind of engine the sport should use.

Ferrari, Formula One's oldest and most successful team, which also gets special payments and enjoys a right of veto, has threatened to leave if it feels that the changes go against its interests.

Main concern

Former F1 racer Wurz said a main concern was the risk of key values being diminished.

The Austrian said the drivers wanted "to prevent any politics or power fights from ultimately compromising on-track performance. The drivers believe unity is fundamental for the sport's success".

Rule changes this year have made the cars faster and harder to drive, a move welcomed by those on the starting grid, while Liberty have brought in experts to address other issues such as improving the show and noise levels.

"We can't be naive about the situation F1 is in, with its complicated governing rules and agreements between various key stakeholders," said Wurz.

"Business decisions and political power fights have damaged the sport enough at exactly such vulnerable times over the last decade."

French racer Romain Grosjean told Reuters in May after being appointed a director of the GPDA that nearly half the grid at that time were not members.

"Missing quite a few of the paddock. Some just don’t give a damn... and I think it’s the wrong point of view," the Haas driver said at the time.

"There’s a big change in Formula One and if we were 20 drivers, out of 20 drivers racing, in the GPDA then we could have a very strong impact and we need to be all united to do something."