Lewis Hamilton and Nico Rosberg
Lewis Hamilton and Nico Rosberg are both fighting to win the F1 Drivers' World ChampionshipGetty

The feud between Lewis Hamilton and Nico Rosberg has taken a turn for the worst after the Brit claimed his Mercedes team mate is "not a real German".

Hamilton, who claimed a memorable victory at the British Grand Prix at Silverstone on 6 July, now lies only four points behind Rosberg in the Formula 1 Drivers' World Championship.

But as their pursuit for the title hots up, Lewis has stoked their personal feud once again after claiming Rosberg, who was born in Wiesbaden, south west Germany, but grew up in Monaco, is "not a real German".

His comments came as Hamilton suggested Rosberg would not be stirred by patriotism at the German Grand Prix in Hockenheim in a fortnight.

"To be honest, Nico has never been in Germany, so he's not really German. I remember when we used to race during karting, he never stood next to a German flag – not ever," Hamilton said.

"We would have to go on the start line and all the drivers would have to stand next to a grid girl in a line. The girls would be holding the flags or a sign saying Hungary or whatever, and he always stood by the Monaco one. He never stood by a German flag. He is German-Finnish-Monaco-esque, or whatever. So it would be great to win in Germany," The Guardian reported.

Signs that the drivers' childhood friendship might be deteriorating emerged after Hamilton joined German team Mercedes in 2013, pitting him against Rosberg, who had been with the team since 2010, to be its main driver.

In the competitive world of F1 driving, Rosberg reportedly became frustrated when team orders prevented him from overtaking Hamilton at the Malaysia Grand Prix last year.

In a so-far Mercedes-dominated season, the pair have battled it out for who finishes highest on the podium, sparking a competitive rivalry that at times has not stopped at the chequered flag.

Earlier in the season, the outspoken Hamilton said his humble upbringing in Stevenage might give him the edge over Rosberg. "Nico grew up in Monaco with jets and hotels and boats and all these kind of things, so the hunger is different," he said.

The lowest ebb of their relationship came in May at the Monaco Grand Prix when Hamilton refused to share podium celebrations with first-placed Rosberg after claiming his team mate sabotaged his drive.

One month later, Hamilton looked to move on from the incident saying the pair had their "ups and downs", but after moving to within touching distance of Rosberg, Hamilton's latest comments may have upped the ante once more.