Conservative MP Zac Goldsmith has urged the leaders of the main political parties to “come clean” over the expansion of Heathrow.

Speaking on BBC’s Newsnight, Goldsmith questioned the independence of an interim report by the Airports Commission on airport expansion to be published tomorrow.

Speculation suggests that the commission will shortlist just three favoured options, each of which includes the construction of at least one new runway at Heathrow.

Goldsmith, whose constituency is Richmond Park and North Kingston in south-west London, has been a vocal opponent of the expansion.

“I think, because of what we know was in the original first draft of this report, irrespective of what is produced on Tuesday, we know that if the parties accept this report in general they are accepting Heathrow expansion,” he said.

“I think they need to come clean about that.”

He continued: “David Cameron himself has to really think very carefully about this.

“Politically, a U-turn on this issue would be catastrophic for him. You have to remember it wasn’t just a few party speeches, David Cameron went to every single constituency affected and stood up and said ‘no ifs, no buts, there will be no Heathrow expansion’.”

Goldsmith said a reversal of positions by the prime minister on the issue “would be an off-the-scale betrayal and he will never be forgiven in west London”.

The Conservative Party has insisted the Davies report is independent. Reports last week suggested Cameron had urged the report’s author Sir Howard Davies to include one option that did not involve Heathrow expansion and that Labour was prepared to drop its opposition to additional runway capacity at the airport.