Plans by Boris Johnson to create a new high-speed rail network across the north of England have been welcomed by the owner of Manchester airport.

But the prime minister cast new doubts over the prospects of a third runway at Heathrow – a scheme he has long opposed – telling MPs that there was “no immediate prospect” of construction starting.

Government sources have said that Johnson has not ruled out attempting to block the scheme even though it has already been approved by MPs, according to The Times.

He pledged in 2015 to “lie down . . . in front of those bulldozers” to stop construction of the two-mile runway.

Heathrow has already gained outline approval from MPs, with the Commons voting overwhelmingly in favour of a third runway in June 2018.

But during the HS2 debate, Munira Wilson, Liberal Democrat MP for Twickenham, branded the new runway proposal “an act of environmental vandalism” and urged the prime minister to “make good his promise of lying down in front of the bulldozers, or far more simply, just cancel the third runway”.

Speaking in the Commons, Johnson said: “I see no bulldozers at present and no immediate prospect of them arriving.”

The so-called High Speed North would be created by combining a proposed new east-west line across the Pennines with the northern part of the £106 billion HS2 line which gained government approval on Tuesday.

High Speed North could open partially by 2035, according to reports.

Work on the first phase of the high speed HS2 line from London to Birmingham and Crewe is due start by April, almost a year late.

It will eventually link the capital with Birmingham, Manchester and Leeds and connect with the trans-Pennine line covering Liverpool, Manchester, Leeds and Newcastle.

Johnson told MPs: “Passengers arriving at Birmingham airport will be able to get to central London by train in 38 minutes, which compares favourably with the time it takes to get from Heathrow by taxi.

“But this is not just about getting from London to Birmingham and back, this is about finally making a rapid connection from the west Midlands to the northern powerhouse to Liverpool, Manchester, Leeds and simultaneously permitting us to go forward with Northern powerhouse rail across the Pennines finally giving the home of the railways the fast connections they need, and none of it makes any sense without HS2.”

Transport secretary Grant Shapps said: “Fully informed by a comprehensive and detailed scrutiny of all the facts, now is the time to drive HS2 forward, alongside a High Speed North plan to give the north and Midlands the capacity and connectivity it vitally needs.

“We are also clear that the project must reform and improve, with clearer accountability and transparency to ensure its incredible benefits are matched by a tight control of costs.

“Our vision for increasing opportunity and prosperity across every part of our country doesn’t stop with HS2.

“We achieve that not only through investing in critical national projects to transform journeys in the future, but delivering on the vital connections people rely on today to ensure no community is left behind.”

Manchester Airports Group said: “Delivering an integrated High Speed North rail network will fast-track the rebalancing of the economy.

“The station at Manchester airport, acting as a hub for the new network, will ensure millions more people across the north and the Midlands have access to high speed rail services and international markets. 

“MAG welcomes the government’s decision today. Planned correctly, HS2 together with High Speed North will provide an integrated high speed rail network direct from Manchester airport to Liverpool, Leeds, Sheffield, Hull and the north-east, and unleash the full potential of the northern economy.

“The sooner High Speed North can be delivered, the better. Starting on its delivery quickly would mean that the north, as well as the south, benefits from new rail connections and capacity as soon as possible.”