Red Bull have insisted that the decision to give world champion Sebastian Vettel a new chassis ahead of the Spanish Grand Prix is not linked to his struggles so far this season.

The German has been largely off the pace of the Mercedes and has even been out-qualified by new teammate Daniel Ricciardo on three occasions in the first four races.

However, while the team's design chief Rob Marshall confirmed that the German was to get a new chassis ahead of the start of European leg of the season, he stressed that the switch was long-planned.

He told Red Bull's website: "Sebastian will get a new chassis for Barcelona, which was scheduled at the start of the season and then the next one will be for Dan at some time around Silverstone.

"Normally we make four or five chassis during the year, maybe six, so it wouldn't be unusual for each driver to change at least once or twice during the year. Normally they would use at least two."

Red Bull are currently fourth in the constructors' standings, 104 points behind Mercedes.