London’s transport system could be overwhelmed by demand when the coronavirus lockdown is eased, according to leaked briefing shared among emergency planners.

The London Strategic Co-ordination Group (SCG) document reportedly stated that London Underground services would be “rapidly overwhelmed” if social distancing was maintained.

It said the capacity of the Tube and bus services would be cut to 15 per cent and 12 per cent respectively, compared with normal levels, if a two-metre space between passengers is enforced, according to the BBC.

The briefing report, which contained a number of scenarios, also warned that lifting lockdown measures could put more pressure on the police to manage crowds, enforce restrictions and respond to an increase in crime levels.

Transport for London would need between three to four weeks to prepare, the briefing also states. Around 7,000 TfL staff are believed to have been furloughed during the lockdown – announced on 23 March, and next due to be reviewed on 7 May.

A TfL spokeswoman said: “When workplaces reopen there will be significant challenges in enabling Londoners to get to and from work while social distancing rules are still in place, as is widely expected to be necessary.”

She added that TfL intends to “build up service levels on the transport network to as close as possible to what they were before the pandemic”.

A spokesman for Mayor of London Sadiq Khan called on the government to engage in “an open and honest conversation” with the public about how restrictions might be eased or changed.

“The easing of lockdown restrictions will undoubtedly pose serious challenges around maintaining social distancing, particularly in London with our high population density and busy public transport network,” said the spokesman in response to the publication of details from the report.

“Whether it’s schools, construction sites or other industries having to stagger their opening hours, or restrictions on the use of the public transport, no options should be off the table,” he said.

“That’s why it is essential we are fully prepared as a country and a city before the lockdown is eased, with a comprehensive package of measures in place to ensure people’s health is protected.”

The London SCG is chaired by the Metropolitan Police and includes other agencies involved in emergency planning in the capital.