The Government has defended its target to ban the sale of conventional diesel and petrol vehicles from 2040, after several cities called for them to be outlawed from 2030.

Cross-party leaders, representing around 20 million people from towns and cities across England and Wales, including London, Liverpool, Manchester, Cardiff, Bradford and Bristol, are among those calling on the Government to introduce the ban earlier than planned.

The collective call from councils follows criticism of the 2040 target by Sir Richard Branson. The Virgin founder, who funds a team in electric motorsport Formula E, says the deadline should be brought forward to 2025, in line with some other European countries.

The Scottish Government has pledged to phase out sales of new diesel and petrol cars by 2032.

However, roads minister Jesse Norman says 2040 is a “sensible compromise”.

“If you look at it overall we’re about as far advanced as almost any government in the world,” he said.

Detail has been lacking about what the 2040 deadline will mean for drivers. The Government says it hopes to publish further information in its Road to Zero strategy in the coming weeks.

But, fresh doubt has been cast on what the 2040 target actually means, reports Fleet News. When the plan was announced last year, the Government suggested that the ban only applied to new vehicles which were not zero-emissions capable.

Business minister Richard Harrington has now told MPs on the Business, Energy and Industrial Strategy Committee that the goal was to achieve “pretty much" zero emission in 2040.

Richard Bruce, director of energy, technology and innovation at the Department for Transport (DfT), who was giving evidence to MPs alongside Harrington, explained that by 2040, all new cars will be “effectively” zero. “It means as close to zero as we can get,” he said.

“There may be scope in certain niche areas for internal combustion engines to persist if they are much more efficient.”

At the time of last year’s announcement, it was understood that hybrid technology, where a small petrol or diesel engine is combined with an electric powertrain, would be exempt.

However, Bruce said: “At the moment, the current hybrid technology would certainly not apply. It would not be appropriate, because it has comparatively short ranges before the engine kicks in and most of the driving is using the internal combustion engine.”

A leak ahead of the publication of the Road to Zero strategy suggests that the Government would ban from sale in 2040 any new cars incapable of travelling more than 50 miles using just electric power.

As a result, today’s volume-selling hybrid cars such as the Toyota Prius and Mitsubishi Outlander PHEV – which cover around 30 miles on electric only – would not qualify.

Bruce continued: “The approach to 2040 is not to pick technologies. It is to talk about the outcomes you want.

“In order to be consistent with the Government’s legally-binding carbon ambitions, we basically need every vehicle to be effectively zero-emission by 2040.

“What that means practically is with a significant zero-emission capability, but it is 22 years away so it would be a bit premature to pick individual technologies now, because we are talking about three product cycles for the car industry and maybe two engine cycles.

“What we are trying to do is give clarity to the industry about the expectations in terms of the outputs or the outcomes. We are not saying ‘this technology, but not that technology’.”

The Government also told the committee, which is running an inquiry into electric vehicles, that there will be no interim targets between now and 2040.

Harrington said: “My view is that the 2040 target is it. We expect the industry to move incrementally towards that. Obviously, it is our job to monitor that progress.”

Committee chairman, Labour MP Rachel Reeves, criticised the Government over the 2040 ban, stating that no guidance on how to meet the ban had been outlined.

She said: “Manufacturers have to make important decisions on technology and investment and need clarity on the meaning of ‘effectively zero’ and what they will be allowed to sell.”