Mark Webber says Pastor Maldonado is one of several drivers on the grid who are not worthy of a Formula 1 seat.
In interview with BBC Radio 5 live earlier this week, former Red Bull driver Webber claimed that the driver "depth has never been weaker", but he has now gone further by saying there too many commercially-driven drivers in the sport.
Speaking to Sky Sports F1, the Australian said: "We know we've got quality at the front, but I just still think there's the swing of the financial [pay] drivers, who are coming to basically decide what teams they want to go to, and also if they're going to stay there.
"There have always been commercially-driven drivers on the grid in F1, don't get me wrong, but in 2002 when I started, or 2010, even mid-90s, I just think there was a sniff more depth in there because there were more chances for the guys who have got the runs on the board [in the junior categories] to get in there purely on results and not with a government behind you supporting you.
Asked if he was referring to Maldonado, who is heavily backed by oil company PDVSA, he replied: "Yeah. Quite a few [others too].
"They need to be treating the sport with more gusto, more professionalism and more purpose of why they're there and not trivialising [by saying] 'oh, I'll just come up the next race and have another go'.
"We used Pastor as an example – there's a few of them who shouldn't be there."
He added: "There are a few of them who are like that and it shouldn't be like that. There just has to be the hunger. You want to see the best guys who are driven, focused, professional, hungry and it means a lot to them."