Jenson Button says Lewis Hamilton's criticisms of McLaren are unjust and insists the squad offers its drivers "phenomenal freedom".
Since moving to Mercedes, Hamilton has intimated that he found McLaren too restrictive and demanding, particularly in regard to sponsor commitments.
"I think the focus on the driver, the driver's performance, and the driver being ready for the job at hand is one thing that I'm noticing is quite a little bit better here," he said of Mercedes.
Button responded that he was "very surprised" by Hamilton's opinion.
"The freedom you have in this team is phenomenal," he said. "In this team, you work, you have to work and you work probably harder than you would in other teams in terms of sponsor requests and what have you.
"This is a Formula 1 team that is not a mass production manufacturer. You need big sponsors to exist in this sport for a team like McLaren and you need to understand that.
"Initially, when I came to this team it was a shock, it really was. After winning the world championship with Brawn I did six sponsor events throughout that year. You come here and it's so much busier.
"But you learn to understand and you learn to adapt and realise that that is part of this job and you need that to succeed."
He said the focus on McLaren's level of sponsor events was misleading.
"The way a driver can help development of a car in this team is amazing," Button said. "You have so much freedom and so much help if you need it. Whatever your issues are, you get help here.
"I have heard so many rumours and read so much about the way this team is and it's so far from the truth. It's not like that.
"It is such an open, friendly team and a team that will do anything to help you if you have any issues."