Boris Johnson said that introducing a toll – expected to be in the region of £2 per car – would be an important way of raising funds for the multi-million pound project.

It came as the Mayor revealed detailed plans to improve the capital’s road network by putting some of the most congested routes underground within ten years.

Five pinch points across London - including at Hammersmith, Barking Riverside and New Southgate - would be tunnelled, freeing up land for parks and public spaces as well as development.