McLaren's treatment of Jenson Button has been "disgusting", according to former grand prix driver Derek Warwick.
McLaren have been unable to choose whether to retain Button, 34, or Dane Kevin Magnussen, 22, to partner two-time champion Fernando Alonso in 2015.
Warwick, who competed at 162 grands prix between 1981 and 1993, added: "Button deserves to stay."
The 60-year-old Englishman also felt that Alonso and Button would make "a great combination".
Warwick, chairman of the British Racing Drivers' Club, said it was a "difficult situation" for McLaren because Magnussen had risen through the ranks and had impressed the team in his debut season in 2014,
"They've invested heavily in Kevin Magnussen," Warwick told BBC Radio 5 live. "He's obviously someone for the future, so I think it's a difficult situation for them."
He added that Button's continued presence at McLaren was important for the British Racing Drivers' Club, which owns Silverstone.
"Our fingers are crossed for Jenson because he brings a lot of people to the British Grand Prix," said Warwick. "That's important for us."
McLaren, who are starting a new engine partnership with Honda next season, have completed a deal for Alonso to re-join the team but will not make it official until they have decided on the identity of the second driver.
The decision is solely that of McLaren chairman Ron Dennis, according to sources.
A McLaren board meeting on Thursday broke up without the team deciding on their driver line-up.
Asked what was causing the delay, a spokesman said: "The team declines to add further details."
He added McLaren would be making "no driver selection announcements until next week at the earliest".
Button, the 2009 world champion, was at a sponsor's event with Magnussen in Scotland on Thursday.
"There are options, but nothing set in stone yet," said the Englishman.
"What I can say is I'll definitely be racing next year - and in a series I'll be very excited to race in - so there's no worry of me not racing next year.
"If it's a new challenge, it will be exciting. If it's in Formula 1, it will be very exciting as well because that will be a new challenge with Honda.
"But I just want to get it done. I want to hear the decision - as we all do - so we can all move on in whatever direction."
Button is keen to stay in F1 and test himself against Alonso, who many observers regard as the best driver in the world.
But he has to decide whether to hang on for a decision from Dennis - which could take weeks - and risk losing his other options, among which is a move to the world endurance championship, with the Le Mans 24 Hours as its centrepiece.
Button added: "It's been an important week, but a really good week. Whatever happens, I will have a great year next year."
Writing on Twitter, Magnussen said of Button: "He is an awesome guy and, no matter what happens next year, I'm cheering for him."