LONDON (AFP) - A UN report has slammed Britain for failing to tackle the "plague" of air pollution, while also warning of Brexit risks, ahead of the body's Human Rights Council opening on Monday (Sept 11).

"Air pollution continues to plague the United Kingdom," said the report by UN expert Baskut Tuncak, to be presented at the rights council in Geneva which runs until Sept 29.

More than 40,000 premature deaths a year are linked to air pollution, noted the report, which argued that through inaction, the government had "violated its obligations" to protect children.

"The Special Rapporteur is alarmed that despite repeated judicial instruction... the United Kingdom government continues to flout its duty to ensure adequate air quality and protect the rights to life and health of its citizens," it said.

The British government has faced a series of legal challenges over its proposals, with a 2015 air pollution plan struck down by the courts for being inadequate.

New proposals, including a scrappage scheme targeting diesel cars, were unveiled in May after the High Court ruled against the government's intention to delay.

But the UN report said the latest plan "does not convey the necessary urgency" and urged the government to implement a "robust clean air plan without delay".

Published against the backdrop of Britain's divorce from the European Union, the Tuncak report praised the bloc for having some of the highest environmental standards in the world which have positively impacted Britain.

Despite government assurances that it will maintain EU environmental standards after Brexit, Tuncak said a lack of clarity on how this will happen has led to a "real danger" Britain will be left without the necessary legal framework.

"The United Kingdom market could risk becoming a haven for 'dirty' industries and a dumping ground for products failing to meet European Union regulations", without matching EU legislation, the report said.

Wading into the subject of Brexit talks, the UN report advised the British government to continue to abide by evolving EU standards despite its exit from the bloc.