Mayor of London Boris Johnson has backed plans to explore the viability of constructing a new ring road beneath the capital in order to ease congestion.

Costing approximately £30 million to build, the Inner Orbital Tunnel is an ambitious scheme that would remove thousands of cars from the streets above. Several other cities - including Paris, Oslo and Boston - already have such infrastructure in place.

The tunnel would link to key routes on the surface, such as the A40, A12, A1 and A2, and feature two new crossings below the Thames.

Transport for London says congestion in the city's central zone could increase by 60 per cent by 2030 unless countermeasures are put in place. In outer areas of the capital, congestion could rise by between 15 per cent and 20 per cent.

Isabel Dedring, deputy mayor for transport, told the Evening Standard the aims of the scheme are "freeing up capacity on the city surface, improving air quality, and reclaiming space for public parks, pedestrians and cyclists".