The rear-wing slot gap was found to exceed the maximum 85mm when DRS was activated with Albon and Sainz excluded from the final qualifying classification.
With the Williams pair officially left with no qualifying laps on the board, Albon and Sainz technically fell short of the 107 per cent rule, which dictates that each car in qualifying must post a lap within 107 per cent of the fastest lap in Q1.
The regulation, which is aimed at ensuring a high competence level among teams, was reintroduced to F1 in 2011 having been first implemented in 1996.
Ahead of Sunday’s race, the FIA has confirmed that the Williams drivers will be allowed to participate in the Singapore Grand Prix.
A stewards’ report on Sainz read: “The Stewards have received a request from Atlassian Williams Racing to allow car 55 to start the Race despite being disqualified from Qualifying.
“In accordance with Article 39.4 b) of the FIA Formula One Sporting Regulations, the Stewards grant permission for car 55, Carlos Sainz, to start the Race, as the driver has set satisfactory times in practice at this Competition.
“The car will be placed on the grid in accordance with Article 42.1 of the FIA Formula One Sporting Regulations.”
An identical statement was issued for Albon, who was previously disqualified from qualifying at last year’s Dutch Grand Prix.
The FIA’s statement comes after James Vowles, the Williams team principal, admitted it was “bitterly disappointing” for both cars to be excluded from qualifying.
And he revealed that the team is “urgently investigating” how the rear wings failed the tests.
In a statement by the Williams team, Vowles said: “During FIA scrutineering after qualifying, the rear wings on both our cars failed DRS slot gap checks.
“As a result, Alex and Carlos have been disqualified from qualifying for tomorrow’s Singapore Grand Prix.
“This is bitterly disappointing for the team and we are urgently investigating how this happened.
“At no point were we seeking a performance advantage and the rear wings had passed our own checks earlier in the day, but there is only one measurement that matters and we fully accept the FIA ruling.
“We have a car capable of scoring points here this weekend and will do everything we can to fight from the back of the grid tomorrow, and will immediately review our processes to make sure this doesn’t happen again.”