Sadiq Khan will in effect ban fracking in London – and warns that extracting shale gas represents a toxic health risk.

In a controversial move, the London mayor will set out in plans to be published this week that councils across the capital should block the exploration, appraisal or production of shale gas via hydraulic fracturing, which sees rocks blasted with water to release the gas.

He will also make clear that any proposals that reach his desk will be thrown out, warning the process could pollute water supplies and put health at risk. The measure will be set out in his draft London Plan.

Q&A What is fracking? Show Fracking, or hydraulic fracturing, is a way of extracting natural gas from shale rock formations that are often deep underground. It involves pumping water, chemicals and usually sand underground at high pressure to fracture shale – hence the name – and release the gas trapped within to be collected back at the surface. The technology has transformed the US energy landscape in the last decade, owing to the combination of high-volume fracking – 1.5m gallons of water per well, on average – and the relatively modern ability to drill horizontally into shale after a vertical well has been drilled. In England, the government placed a moratorium on fracking in November 2019 after protests, legal challenges and planning rejections. A year earlier, the energy company Cuadrilla was forced to stop work at its Preston New Road site in Lancashire twice in four days due to minor earthquakes occurring while it was fracking. The tremors breached a seismic threshold imposed after fracking caused minor earthquakes at a nearby Cuadrilla site in 2011. In March 2019 the high court ruled that the government's fracking guidelines were unlawful because they had failed to sufficiently consider scientific evidence against fracking.

Khan has agreed with campaigners who have warned that the fracking process can generate toxic silica dust, which can cause chronic lung damage, as well pollutants that worsen neurological problems, from dizziness to seizures. The levels of water required for fracking could also lead to shortages, the plan will say.

While there are no current fracking applications in London, a company said over the summer that it was looking at one site under an industrial estate in the capital that could have deposits “worth millions”.

Khan said there was “absolutely no place for fracking in London” and applications must be refused. “The harmful, negative impact of the use of fossil fuels on the environment and on the air we breathe is well known,” he said. “We must instead focus our resources on developing technologies for the efficient extraction of clean, renewable forms of energy, rather than coming up with more ever innovative ways to keeping burning fossil fuels.”