The FIA have issued another Technical Directive to the teams to clarify what will and will not be permitted as they clampdown on team radio transmissions from this weekend’s Singapore Grand Prix.

FIA Race Director Charlie Whiting wrote to all 11 teams last week stating that radio communication relating to the performance of the driver and the car would be banned with immediate effect.

He has since given further clarification to the teams as to what will be banned heading forward, including some rules that will be only introduced from the Japanese GP onwards.

Coded messages will be banned and the wording - "any message that appears to be coded" – should make it easier for the stewards to penalise anyone they suspect to be circumventing the rules.

The clampdown on performance related messages over the radio will also apply to pitboards and pit-to-car telemetry that can tweak settings remotely is also banned.

Messages that will still be allowed:

- Acknowledgement that a driver message has been heard.

- A competitor’s lap time.

- Their own lap and sector time.

- Gaps to a competitor during a practice session or race.

- Information about a competitor's likely race strategy.

- Tyre choice at next pitstop.

- Front-wing adjustment at their next pitstop.

- The number of laps a competitor has done on a set of tyres during a race.

- A competitor’s tyre compound.

- Being told to increase their pace (E.g. “Push hard” or “push now”).

- Who they are likely to be racing (E.g. “You will be racing XX”).

- Warning of a puncture.

- Information on yellow and blue flags.

- Safety Car deployment.

- Problems with a competitor’s car.

- Team orders.

- Laps remaining.

- Help with finding a gap in qualifying.

- DRS enabled and disabled notifications.

- Infractions by team, driver or competitor (E.g. running off track, missing a chicane, time penalty).

- Track information (E.g. Wet track, oil or debris at certain corners).

- Damage to the car.

- Reminders to check for white lines leaving and entering pits and weighbridge lights.

- Weather information.

- Test information (Eg. Set speed runs for aero-mapping).

- When to pit.

Messages that are banned:

- Sector time detail of a competitor and where they are faster or slower.

- Adjustment of powerunit settings.

- Answering a driver’s direction question (E.g. "Am I using the right torque map?").

- Level of fuel saving needed.

- Any message that appears to be coded.

- Information on tyre temperatures and pressures (from Japan onwards).

- Balancing the SOC (state of battery charge) or adjusting it for performance.

- Number of burn-outs required prior the race.

- Warning of brake-wear or temperatures (from Japan onwards).

- Learning of gears from gearbox (from Japan onwards).

- Start maps related to clutch position, for race start and pit stops.

- Information on clutch maps or settings (E.g. bite point).

- Brake balance and brake-by-wire information.

- Adjustment of gearbox settings.

- Information on fuel flow settings (unless requested to do so by Race Control).

- Adjustment of powerunit settings to de-rate system.

- Selection of driver default settings (unless there is a clearly identified problem with the car).

- Information on differential settings.

Following last week’s announcement Mercedes boss Toto Wolff has described the changes as “controversial” stating that “there will inevitably be some controversy”.

McLaren’s Eric Boullier added that the new Technical Directives will further complicate what is already a difficult grand prix for the teams in Singapore.

“We are still evaluating the full consequences of the new interpretation of Article 20.1 of the FIA Sporting Regulations, but, as a team, we will of course find a solution that works and which follows this new interpretation,” the Racing Director said.

“Singapore is a difficult race to manage under normal circumstances, so this will definitely add an extra dimension to our preparations.”