Parents have been urged to “take care” when going outside with a baby in London because of air pollution levels.

In a report issued by Plume Labs, a firm which specialises in raising awareness of environmental hazards via a mobile application, it labelled the level of air pollution as “high”.

Its hour-by-hour readings on Friday included pleas for people to “take it easy” during sport and when eating outside, and also ranked the air quality as half as healthy as the annual average.

“We are not saying that you should not go out with your baby," said Romain Lacombe, chief executive and co-founder of Plume Labs.

"But leave the car at home, stay away from major roads and high traffic areas, and keep an eye on live pollution updates.”

The news follows a climate change report claiming that 55bn tonnes of carbon will be released into the atmosphere, and that temperatures will increase by 1C, before 2050.

The paper’s lead author said global warming had slipped beyond the “point of no return”.

Four major world cities also this week pledged to ban diesel before 2025.

Environmental lawyer Alan Andrews, the clean air project leader at ClientEarth, told The Independent: “Diesel emissions are bad news for climate change and human health and the nearer we can get to phasing it out and moving towards electric cars and other alternatives power sources, the better.

What's the effect of global warming on our seasons?

“We need to get away from fossil fuels because diesel is killing thousands a year.”

A considerable number of users have posted their pictures of apparent smog over the London cityscape on Twitter over the last couple of days.