|Hungarian Grand Prix|
|Dates: 22-24 July Venue: Hungaroring|
|BBC Coverage: Preview - Thursday, 21 July (BBC Radio 5 live 21:00 BST); race commentary - Sunday, 24 July (build-up on BBC Radio 5 live from 12:00, race starts at 13:00). Live text commentary of all practice sessions, qualifying and the race on the BBC Sport website|
Restrictions on radio communication between teams and drivers have been strengthened in the build-up to Sunday's Hungarian Grand Prix.
Any message informing a driver of a car problem "must include an irreversible instruction to return to the pits to rectify the problem or to retire".
The ruling from governing body the FIA comes after Mercedes broke radio rules at Silverstone last time out.
Nico Rosberg was demoted from second to third after a 10-second penalty.
The new ruling means teams will not be able to make calculations about the potential time loss of any post-race penalty in giving instructions to a driver.
Instead, the requirement for a driver to return to the pits to rectify a problem he does not know how to solve himself will automatically result in losing a significant amount of time.
The new FIA ruling also stresses that any change a team tells a driver to make must be with the aim of repairing a problem and not improving performance.
A note issued to the teams says any instruction "must be for the sole purpose of mitigating loss of function of a sensor, actuator or controller whose degradation or failure was not detected and handled by the onboard software".
It adds: "It will be the responsibility of any team giving any such instruction to satisfy the FIA technical delegate that this was the case and that any new setting chosen in this way did not enhance the performance of the car beyond that prior to the loss of function."
Teams have said that the radio rules need to be re-thought as it is wrong to penalise a driver for fixing a serious problem on his car.
Vettel unimpressed with new rules
Ferrari's Sebastian Vettel came out strongly against the new rules when asked about them in the Hungaroring paddock on Thursday.
The four-time champion used an expletive to describe the FIA's stance on radio communications, adding: "I think it's a joke. I looked at the [Silverstone] race afterwards and I found as a spectator it was quite entertaining to hear a driver panicking on the radio and the team panicking at the same time.
"It was the element of human being in our sport that is very complicated and technical, so I think that's the wrong way.
"If you want to change it, you should change the cars. All the buttons we have on the steering wheel are there for a reason. If you just look at the 1995 steering wheel it was a lot simpler because the technology was simpler.
"It's not our mistake that the cars are so complicated these days that you need a manual this big and a steering wheel full of buttons to operate it."
Vettel's remarks inadvertently address the issue at the heart of the thinking of governing body the FIA in strengthening the ban.
The FIA believes the cars have become unnecessarily - almost wilfully - complicated and had hoped the restrictions on radio transmissions already introduced for this season would encourage them to simplify the control systems.
The fact that it has not worked is not a reason, the FIA believes, to re-think the radio ban, rather a reason to keep pushing the teams in that direction.