F1 tightens cooperation rules, clears Ferrari - Haas

In a statement issued at the season-ending Abu Dhabi Grand Prix, in response to questions posed by champions Mercedes, they also made clear that Ferrari would face no consequences for their work this year with the new U.S.-based Haas team.

"No retrospectivity shall apply," they said in a detailed document.

The stewards said they would recommend to the governing FIA that any future 'potential competitor' be bound by the rules once their application to enter the championship had been accepted rather than at the moment of official entry.

The championship entry list, for the season that starts next March, will be published in December but Haas's application was accepted long ago.

Haas, who will use Ferrari power units and whatever parts and components the regulations allow, are due to make their debut next season.

Ferrari, who failed to win a race in 2014, have made significant progress this season and have emerged as the closest rivals to Mercedes.

There have, however, been suspicions that the Italian team have benefited from their relationship and the wind tunnel activities of North Carolina-based Haas in pushing their aerodynamic development.

In the statement, the stewards made clear that the main aim of the rules was "to prevent an escalation of the costs associated with research particularly...in the area of aerodynamic testing".

Mercedes had denied targeting Ferrari in seeking clarification from the stewards about 'ambiguities' in the technical regulations.

"We are looking at 2016, and especially in consideration of 2017 rules where the car might be completely different, about the scope of development we could be having with another team, about sharing resource," motorsport head Toto Wolff had said.

He warned, however, that unless the rules were clarified there could be an "arms race" between teams trying to sign up as many cooperation partners as possible to speed up development of their cars.

(Editing by Clare Fallon)