Sir Keir Starmer and 16 of his ministers including seven who attend Cabinet were urged “not to U-turn” on their previous opposition to a third runway at Heathrow.
The now Prime Minister voted against expanding the west London airport when it was being pushed through by the Conservative government in June 2018.
It was also opposed then by the current Environment Secretary Steve Reed, Net Zero Secretary Ed Miliband, Culture Secretary Lisa Nandy and Northern Ireland Secretary Hilary Benn.
Chancellor Rachel Reeves is reportedly set to signal within weeks support for a third runway.
But her deputy Darren Jones, Chief Secretary to the Treasury, her sister Cabinet minister Ellie Reeves, and development minister Anneliese Dodds, who all also attend Cabinet, also voted against a bigger Heathrow six years ago, as did nine other ministers.
Ms Reeves was challenged in the Commons over whether she backed a bigger Heathrow, which could see the number of annual flights jump from 480,000 to more than 700,000.
“Residents of my constituency of Richmond Park will be extremely concerned to read the news this morning that the Chancellor plans to announce next week the expansion of Heathrow airport,” said Liberal Democrat MP Sarah Olney.
She urged the Chancellor to give a “yes or no” response as to whether the Government backed a third runway.
Ms Reeves responded: “I’m not going to comment on leaks.
“But what I would say is this Government is absolutely committed to growing our economy and making this a great place for business to invest and trade in.”
Downing Street brushed away questions on whether the Government was shifting towards backing another runway at the west London airport.
The Prime Minister’s official spokesman said: “I’ve seen the speculation, I can’t comment on the speculation.
“But you know that we have said before that as a Government we are determined to get our economy growing and secure the long-term future of the UK’s aviation sector.
“We have also said that any airport expansion proposals must demonstrate they contribute to economic growth...while remaining in line with existing environmental obligations.”
Green peer Baroness Jenny Jones warned the Government against “eco-stupidity and eco-ignorance” on a third runway.
She added: “I just don’t see why they would do a U-turn when we all know that it is really bad for residents and the planet.”
Six years ago, 94 Labour MPs opposed to go-ahead for expanding Heathrow in a showdown vote on the National Policy Statement on Airports, but it was approved by 415 votes to 119.
Labour MPs who voted against the expansion included Industry Minister Sarah Jones, Emma Reynolds, Economic Secretary to the Treasury, Foreign Office ministers Catherine West and Stephen Doughty, Housing Minister Matthew Pennycook, Roads Minister Lilian Greenwood, Children and Families Minister Janet Daby, Education Minister Stephen Morgan and Food Security Minister Daniel Zeichner.
Former London Mayor Boris Johnson, who was Foreign Secretary at the time and a long-time critic of a third runway, was on a trip to Afghanistan on the day of the vote, which sparked accusations that he had deliberately missed it, but eight Tory MPs opposed the expansion.
The current Labour government is yet to receive a Development Consent Order for the third runway project to proceed.
