​Brexit has reduced the amount of travel in London, a top public transport executive has said.

Alex Williams, Director of City Planning for Transport for London, told a conference in the capital: “Total trips in London, a leading indicator of economic activity, are going down partly because of the uncertainty of Brexit.”

He told The Independent: “Our issue is that we don’t know if this is a kind of blip or part of a longer-term trend.

“It’s a one per cent reduction on the Tube, which is a great bellwether for the Bank of England about how the economy is going.

“It could be Brexit, it could be the terrorist incidents in the summer affecting domestic tourism in particular. But our concern is that five months into the financial year, that seems to be continuing.”

The conference, organised by the Westminster Energy, Environment & Transport Forum, is discussing the proposed expansion of Heathrow. Five years ago this month, the Coalition Government set up the Davies Commission to consider options for expanding airport capacity in south-east England.

In July 2015, Sir Howard Davies’ Airports Commission unanimously recommended a third runway at Heathrow. Its findings were approved last year, but consultations are continuing. Unless the National Policy Statement is approved by Parliament by next summer, the planned completion of the runway in 2025 will be jeopardised.

Emma Gilthorpe, Executive Director Expansion for Heathrow, called for faster progress. She told The Independent: “With Brexit it is even more important than we not only send a message that we’re open for business, but that we also have the mechanics to deliver links to long-haul markets that we may not do business with today, but we will absolutely need to do business with tomorrow.

“There was a very strong economic case before. I think with Brexit the urgency increases.”