Sebastian Vettel has hit out at championship leader Lewis Hamilton for his 'unreasonably' slow formation lap ahead of the Russian Grand Prix in Sochi.

With Rosberg starting on pole position, second place Hamilton slowed to a crawl on the run to the grid in an apparent tactical move against his Mercedes team-mate. It is an approach that would prompt an irked response from Vettel at the time, the four-time champion making his feelings known by pulling alongside in an apparent attempt to speed him up.

With Hamilton then slowing the field down again just prior to a safety car restart - creating a concertina effect behind him -, Vettel says he is unimpressed with the 'aggressive' strategy and has urged stewards to 'look into it'.

"I thought he was going unreasonably slowly," he said. "There was no reason to go that slow. If you want to pack up the field you can do it earlier and not in the very last bit. I tried to tell him 'go' because it is ridiculous.

"You need to be aware that if you stop suddenly and aggressively, five cars back it has a much different effect than to the car just behind. The restart was not the way to do it. There is a rule. At the start of the formation lap I was trying to show him 'go'.

"It was both of them [Nico] going slow and the restart was similar so maybe they need to look into it again."

It is not the first time the Mercedes' drivers have come in for criticism over slow formation laps, with Felipe Massa complaining in 2014 that both drivers drive unnecessarily slowly on the warm-up lap creating problems for those behind.

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