McLaren's technical director Paddy Lowe has insisted that Red Bull's aerodynamic exhaust development is perfectly within the rules of Formula 1.
Although rule changes were supposed to halt such exhaust developments, Lowe has admitted that all major teams are working on the area.
"To the extent [Red Bull's progress] has been down to exhausts, I'd consider that to be fair game," he said.
"All leading teams are working in that area. I don't have a problem with it."
McLaren are 101 points behind Red Bull in third place in this year's constructors' championship.
