Four-times Formula One world champion Alain Prost fears Nico Rosberg and Lewis Hamilton risk damaging their relationship in the heat of this year’s intense fight for the title.

Hamilton and Rosberg have known one another since their karting days, even working as team-mates, before re-uniting last year following the former’s arrival at Mercedes.

The duo have always been civil and cordial towards one another, but as time has worn on this season that has shown signs of slowly changing.

Hamilton’s four successive victories, following Rosberg’s early win in Australia where the Briton retired, have propelled the 29-year-old into a three-point lead over the German.

Rosberg has been forced to settle for the runner-up spot behind his team-mate on each occasion, and it is clear that this has rankled.

Undeniably their battle for supremacy at present lacks the ferocity of F1’s bitterest intra-team rivalry between Prost and Ayrton Senna in 1988-89 when the duo raced for McLaren.

But asked by PA Sport about the Mercedes scrap, Prost smiled and said: “They are having a nice battle at the moment. It’s good for F1, and with one team dominating they are letting them race, although I don’t know how long that’s going to be the case.

“The good thing is if they continue to dominate the same way then they can let them race until the end. For sure, it’s a risk to their relationship.

“On the other hand, if Red Bull come back and perform better they can decide a few races before the end and say ‘Okay, we’re going to have a number one and a number two’.

“That’s going to be a very complex situation because the last race is worth 50 points. That is a rule I do not like, but maybe it will help the championship, you never know.”

With Hamilton at present in the ascendancy, Prost has revealed he had a chat with Rosberg following the recent Spanish Grand Prix.

Hamilton won from pole, but conceded Rosberg – who finished just 0.6secs adrift after more than 300 kilometres of racing – was the better man over the course of the weekend.

“I talked to him on Sunday night, and there are a few things he can do,” revealed Prost.

“First of all he understands he needs to be on pole and start the race first. There were at least two races where he was a little bit quicker than Lewis, but you know how difficult it is with the same car.

“It’s very tight but just because Lewis has won four times that doesn’t mean things cannot change.”