Research by the group, which opposes a third runway, suggests 31 of the capital's 73 MPs, are known to be opponents of the plans.
Chair of HACAN, John Stewart said: "Once the views of all London’s MPs are known, it is highly likely that a majority will be opposed to Heathrow expansion.
"Of themselves they may not stop it but they could act as a very awkward block to a new runway ever seeing the light of day, particularly given the fact that the new Government doesn’t have a majority of seats in parliament.”
MPs included in the list are Ruth Cadbury, MP for Brentford and Isleworth, Seema Malhotra, MP for Feltham and Heston, and Rupa Huq, MP for Ealing Central Acton.
In response to the claims, Back Heathrow executive director, Parmjit Dhanda, said: “Recent polling shows that 71% of Conservative MPs and 74% of Labour MPs back Heathrow expansion.
“In areas near Heathrow many pro-expansion MPs were elected yesterday including Stephen Pound, Virendra Sharma, Gareth Thomas, Tan Dhesi and Kwasi Kwarteng.
“It’s no surprise that there is such strong public and political support for a new Heathrow runway considering the huge number of new jobs, apprenticeships and opportunities that will come to the local area once the UK’s largest port is expanded."
The decision on whether to expand Heathrow Airport will be voted on by parliament either later this year or in 2018.
Keep up to date with the latest news in west London via the free getwestlondon app.
You can set up your app to see all the latest news and events from your area, plus receive push notifications for breaking news.