"There will be a full and proper consultation," Grayling said. "That is the process we will follow, we will do it in as timely a way as we can."

The government has previously said the whole approval process would be completed by late 2017 or early 2018.

Grayling also said the government would be publishing new evidence relating to the air quality implications of the project in the coming days. He also said Heathrow had committed to using British-made steel in the expansion.

(Reporting by Kylie MacLellan and William James; editing by Costas Pitas)