Boris Johnson has called the expansion of Heathrow a “fantasy” that should be consigned to the “dustbin”.

His comments follow the announcement that the foreign secretary will be excluded from the cabinet committee to decide on airport expansion – a move seen as an indicator Theresa May will approve a new runway at the west London hub.

Johnson warned it will be the taxpayer that has to foot the bill. He told The Daily Telegraph: “As I’ve advocated for many years Heathrow expansion is the wrong choice, and if it is chosen it simply won’t get built,” he said. “The massive costs and enormous risks mean it’s undeliverable, and the taxpayer will be saddled with the bill for failure.

“While we are finding this out our international competitors will be further extending their competitive advantage over us. We need to consign this Heathrow fantasy to the dustbin. We need a better solution,” Johnson added.

The long-awaited decision on airport expansion is politically sensitive given the divisions in the Conservative Party about the issue.

The former London mayor has campaigned against Heathrow expansion and saw his own idea, Boris Island, rejected by the Airports Commission.

A Downing Street spokeswoman said membership of the Cabinet committee will be confirmed “in due course”.

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