A spokesman said a lack of vehicle emissions data made its claims the UK will meet legal air quality levels by 2025 unreliable.
Ongoing consultation on the Government’s draft Air Quality Plan, which included the predictions, ‘may be legally flawed’, the spokesman said.
Gatwick’s Airports Commission Director, Alastair McDermid said: “We all want to see our air quality improving but the ongoing scandal on vehicle emissions makes it difficult to know what to believe.
“Without publishing their assumptions on vehicle emissions, the Government risks eroding public confidence even further.
“Air quality is such an important issue for human health that the Government’s plans need to be realistic, transparent and properly scrutinised.”
Gatwick Airport’s ‘interim response’ to the consultation stated the Government made ‘dramatic’ revisions to its air quality predictions from 2014.
Mr McDermid’s letter to the Department for Environment Food & Rural Affairs (Defra) stated: “In the absence of the supporting Technical Report it has not been possible to understand what has changed both in respect of modelling approaches and assumptions or measures to bring about these predicted improvements.
“It is therefore not possible to understand fully, or to comment with confidence on the accuracy or validity of the assessments or the soundness of the Air Quality Plan, or to comment properly on the consultation at this time.
“We urge Government to make the Technical Report available for consideration at an early date and to allow sufficient time for this to be considered.
“Otherwise, the validity of the consultation must be in question.”