Transport secretary Chris Grayling has confirmed that a long-delayed decision over where to site a new runway in the south-east will be taken “shortly”.

Speaking on the eve of the Conservative Party conference in Birmingham, Grayling told the BBC: “You will get an announcement shortly. We haven’t taken the decision yet.”

He also refused to rule out granting a free vote to Conservative MPs on the issue of airport expansion, saying “decisions about parliamentary handling… have not yet been taken”.

The decision has been debated for years and was delayed most recently by the Brexit vote.

Heathrow had looked close to being the winner, after the Airports Commission recommended a third runway in July last year.

But the decision was postponed for further studies in December.

And following the UK’s vote to leave the European Union in June, it was decided to delay the final go-ahead until October.

The three options in contention are a third runway at Heathrow, extending one of Heathrow’s existing runways and a new runway at Gatwick.

Grayling said he has spent the summer looking at the plans.

“They’re all very well crafted proposals, they’re all very interesting, they’ve all got great potential. We need to decide which is best for Britain.”