The Italian company said in a statement at the Japanese Grand Prix that it had no say over which tyres were allocated to whom, or when they were used.
Mercedes were eclipsed by rivals Ferrari and Red Bull in qualifying in Singapore, after Lewis Hamilton and Nico Rosberg had taken pole position in all 12 previous grands prix, and also in the floodlit race won by Ferrari's Sebastian Vettel.
Some of the more extreme theories circulating within the paddock after qualifying and the race wondered whether Mercedes might somehow have been given different tyres to their rivals to slow them down.
Even Mercedes motorsport head Toto Wolff admitted to a momentary doubt: "For a moment I thought 'Have Pirelli given us a different tyre to the others?'" reports quoted the Austrian as saying.
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"I’m not saying that it happened, just that I thought it," he added.
In a statement explaining how the tyres are marked at their Turkish factory with embedded and traceable bar codes that cannot be swapped, Pirelli said their process was designed to be tamper-proof and random.
"Once the production run for each grand prix is finished, the Izmit factory sends a list of the bar codes to Pirelli's logistics and distribution hub at Didcot in the United Kingdom," the Italian manufacturer said.
"There, Pirelli's system randomly groups the bar codes into blocks of four, comprising two rears and two fronts, which will make up a tyre set. This list of blocks is then sent to the (governing) FIA.
"The FIA subsequently allocates blocks of bar codes -- and therefore sets of tyres -- to each individual car at random," said Pirelli.
Motorsport head Paul Hembery added: "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.
"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."
(Reporting by Alan Baldwin, editing by Amlan Chakraborty)
