Airport operator BAA has manipulated noise and pollution data to meet government specifications in order to win approval for a third runway at Heathrow.
According to UK newspaper The Sunday Times, BAA presented the government with amended figures that underestimate the damaging side-effects of a new runway.
Shadow Treasury Minister and MP for Putney, southwest London, Justine Greening says documents she obtained under the Freedom of Information Act show BAA's involvement was inappropriate and should be investigated.
The papers include memos between BAA officials and a senior civil servant in the Department for Transport (DfT), who had been tasked with proving the runway could be built without any adverse effects on the environment.
BAA suggested initial findings be dumped in favour of "reforecast" figures, including manipulation of flight data, carbon emissions and noise levels.
The newspaper says BAA predicted car engines would be so clean by 2030 that carbon emission around Heathrow would not be higher than they are today even with an additional runway, and did not include international arrivals in carbon emission predictions.
BAA says although it provided some data, the DfT was responsible for the research and resulting report.
Government watchdog the Environment Agency says the report is flawed and incomplete.
"There are arguments for postponing irreversible investment decisions in the face of uncertainty," it says.
Construction of a third runway will increase flight numbers from 480,000 to 720,00 per year by 2020.
Costing up to £9bn, the runway will boost passenger numbers from 60 million a year to 100 million.
The DfT is expected to announce its decision on the runway later this year.
By Elizabeth Clifford-Marsh
Twitter