Campaigners against the Cricklewood rail super-hub have been left disappointed after Sadiq Khan refused to intervene.

In February, Barnet Council approved the project for an aggregate transfer station in Edgware Road.

While it’s in the borough of Barnet, it is also near its borders with both Camden and Brent.

Councillors from all three boroughs objected to the plans, and raised concerns about the effect on pollution and traffic if it went ahead.

Neighbours sent about 4,000 objection letters to Barnet Council saying 450 extra lorries every day would create noise, pollution and traffic jams.

The mayor of London has the power to “call in” applications that meet certain criteria and can approve or turn them down.

But having looked at updated plans, Mr Khan believes they comply with the London Plan and draft London Plan, meaning Barnet’s decision will stand.

Councillor for Mapesbury Lia Colaccio, who has campaigned against the hub, said she wasn’t happy with the decision not to call it in.

“It’s not what we would have wanted.” But she added: “It’s not a political decision – it’s been done on planning grounds.”

The letter from Mr Khan to Barnet Council said: “I am content to allow Barnet Council to determine the case itself, subject to any action that the [communities secretary] may take, and do not therefore wish to direct refusal or to take over the application for my own determination.”

Campaigners are now pinning their hopes on a public enquiry “backstop” which will be the final way the plans can be halted.

Cllr Colaccio, who is also founder of the Coalition for a Sustainable Brent Cross, said: “We’ve asked the Department for Communities and Local Government to call it in and have a public enquiry. That’s our backstop. That will be our last chance so we will be asking the secretary of state to intervene.

“We have to try everything because this will affect generations and we’ve got to look at every option.”

A decision on whether communities secretary James Brokenshire will look at the request for an inquiry is expected to be made over the next few months.