The Formula 1 paddock remains split on the issue of radio restrictions, as the FIA further tightened the rules ahead of the Hungarian Grand Prix.

In a shock move following recent criticisms, the governing body on Thursday revealed a further clarification.

The headline is that a driver like Nico Rosberg at Silverstone who is told about a problem must now pull into the pitlane during a race to have it fixed.

"The rule is now clearer than before," a Mercedes source told Auto Motor und Sport.

Williams's Valtteri Bottas isn't sure, arguing that some teams may choose to ignore the pitlane instruction and instead push for a Rosberg-like post-race time penalty.

"At the moment it looks like it's better to take the penalty," said the Finn.

Ferrari's Sebastian Vettel pulled no punches at all, blasting the "bullshit" radio rules.

Force India team manager Andy Stevenson is also confused, revealing: "We checked all the radio messages after Silverstone and there were more than 15 cases that should have been punished too."

He also warned that the new clampdown will drive up costs, with engineers now having to rewrite some software.

Williams technical chief Pat Symonds is also surprised with the FIA's latest rule tweak, declaring: "We wanted the radio ban to be somewhat relaxed, so what does the FIA do?

"They make the rules even more strict."

Practice for the weekend's race gets underway tomorrow.