Hamilton's 'unauthorised' engine use in Spain behind feud with Rosberg: Report

The use of an unauthorised engine mode by Mercedes ace Lewis Hamilton to hold off his teammate Nico Rosberg in this year's Spanish Grand Prix may reportedly be the reason behind their feud, which exploded publicly in Monaco.

It is understood that the pair are not on speaking terms as they barely offered one another a glance on the podium in Monaco Grand Prix, declined to shake hands and did not congratulate each other.

According to the Sydney Morning Herald, protecting a narrow lead in the closing stages of the Spanish Grand Prix, Hamilton turned up his engine performance to maximum without the permission of bosses on the pit wall and he was forced to apologise to his Mercedes team.

However, Hamilton claimed that the same thing happened to him at the Bahrain Grand Prix, which he blamed on Rosberg.

Toto Wolff, Mercedes' head of motorsport, confirmed that both drivers would no longer have the freedom to adjust their own engine settings.