Voters may turn their back on long-serving Labour MP Ann Keen at the next general election if her party approves the controversial third runway for Heathrow, a new report has claimed.
A recent survey by environmental group Greenpeace suggested constituencies under the flightpath will swing from Labour to the Tories if the Government opts to back the airport's latest expansion plans.
Long-serving Brentford & Isleworth MP Ann Keen was this week named as one of the west London MPs who could lose their seats.
A poll of 1,000 adults in the area suggested a swing away from Labour of around five per cent if the runway is given the go-ahead.
Greenpeace campaigner Vicky Wyatt said: "Building a third runway would be a political disaster for the Government. They'd leak votes in west London and lose key constituencies. If such a swing was repeated across a wider area, then many more Labour MPs could lose their seats.
"The environmental case for blocking this third runway is overwhelming, and the business case is deeply flawed, and now we can see it would be a political nightmare for the Government too."
Almost a quarter of the constituents polled said they would be less likely to vote Labour if the additional runway is built.
Such a swing would see the Government lose seats in Battersea, Ealing Central & Acton, and Hammersmith, and they would have their lead in Feltham & Heston and in Ealing North slashed by half, according to Greenpeace.
But a spokesman for Mrs Keen and her husband Alan, who serves as MP for Feltham & Heston, insisted the electorate would vote on a 'wide range of issues'.
He added: "Ann and Alan's opposition to Heathrow expansion is long-standing, and well-known in their constituencies.
"This is a major issue and, like many of their constituents, Ann and Alan feel very strongly about it. However, as constituency MPs with postbags brimming with casework, there are literally hundreds of other issues that concern people too."
A Government decision on the extra runway was originally expected in December but has been delayed until later this month.