Labour is expected to drop its formal support for a third runway at Heathrow today.

However, Labour confirmed that it would give its MPs a free vote in a sign of the split in the party on Heathrow expansion.

The party will announce that the £14 billion scheme fails to meet the four key tests it established as a condition for parliamentary support, The Times reported.

An analysis of the government’s National Policy Statement, the legislation that will pave the way for a third runway, showed that it failed to satisfy any of its targets on carbon dioxide emissions, noise, benefits to all regions and “ultimate deliverability”.

Shadow transport secretary Andy McDonald said there were “unanswered questions” over the funding of the project.

The decision comes days before MPs are finally due to have a vote on the NPS in Parliament next Monday.

There is strong support for a third runway from Jeremy Corbyn’s union allies, including Len McCluskey’s Unite.

Research by Heathrow has suggested that up to 75% of all MPs support a third runway, including the SNP, the DUP and a sizable number of Conservative and Labour MPs.

A free vote for Labour means that the third runway is almost certain to pass a parliamentary vote.

However, the decision to drop the party’s formal support for the runway will be seen as a significant step with the potential to sway some MPs, according to the newspaper.

The party has formally backed a third runway for at least 15 years.