Pirelli has moved to deny it had an involvement in Mercedes' unexpected struggles during the Singapore Grand Prix, saying it has no involvement in the allocation of its tyres during a race weekend.

Mercedes' downturn in pace in Singapore - a swing of two seconds per lap race-on-race - left engineers perplexed, not least because it is yet to determine entirely why it suffered such a slump compared with Ferrari and Red Bull.

Despite this, Mercedes says it is confidence the time lost can be explained predominantly by its failure to make the Pirelli tyres work around the Marina Bay Circuit, raising speculation that a more underhand reason was at play.

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However, Pirelli has dismissed this assertion, issuing a statement to explain the 'barcode allocation system' which randomly groups the tyres into blocks of four - two front, two rear - to make up a tyre set before being sent on to the FIA, which distributes them.

An effort to remove itself from any suggestion that it has any influence on which tyres are used by certain teams, Pirelli maintains complete confidentiality when it comes to allocation.

"Deciding which tyres are allocated to which teams, or when they are used, is a job taken care of entirely by the FIA once the tyres have left the factory," said Paul Hembery. "It is just another way that impartiality can be ensured among all the teams, which has always been a huge priority for us as exclusive tyre supplier. The way that our team engineers work also respects this confidentiality, which is constantly of paramount importance."