David Cameron has come under withering attack from the European Commission, accused of failing to get to grips with the levels of air pollution in Britain after he labelled the smog afflicting parts of the country a "naturally occurring weather phenomenon".

As ambulance services in London reported a 14% spike in 999 calls due to breathing problems and forecasters predicted the poor conditions would subside by the weekend, Cameron urged people to take heed of warnings from the Met Office and public health officials. "It is unpleasant, and you can feel it in the air … I didn't go for my morning run. I chose to do some work instead. You can feel it.

"But it's a naturally occurring weather phenomenon. It sounds extraordinary, Saharan dust, but that is what it is."

His comments, to the BBC, were attacked by the opposition and questioned by experts who said that underlying air pollution from industry and cars posed the more significant danger to public health. But the most stinging criticism came from the European Commission whose environment spokesman, Joe Hennon, described the prime minister's comments as "more than disappointing" and of showing a "clear misunderstanding" of the air pollution crisis facing the UK.

"It's more than disappointing because you have 400,000 people across the EU dying each year – including 29,000 in the UK – because of air pollution," Hennon said. "To say this is a temporary issue caused by Saharan dust shows a clear misunderstanding of the air pollution issue. Next week you will still have the same levels of air pollution in London and unless governments do something about that we will still have these problems."

In February, the European commission began legal action against the UK for failing to reduce levels of nitrogen dioxide (NO2) air pollution despite 15 years of warnings. The EU environment commissioner, Janez Potocnik, has singled out Britain for its "persistent" breaches of the air quality directive. Hennan, the European commission spokesman for Potocnik, said: "It's clearly an issue you would expect any government to deal with if it's serious about protecting the health of the general public.

"It shows that the problem is not yet understood and one of the reasons we're taking legal action against the UK is that they've not met the targets they agreed to. If I was living in the UK then I would not be happy about that."

The London mayor also played down the issue, telling ITV News that people needed to have some balance: "I cycled this morning and it seemed perfectly fine to me. I think we need to keep a little bit of a sense of proportion. I cycled perfectly happily around today." His remarks prompted derision from Brussels. Hennan said: "It suggests to me their advisers maybe haven't done enough research. It's very clear the UK has a serious problem – not just the UK but half the EU countries – and it's a fairly glaringly obvious one, and all you have to do is read some analysis of the issue."

The Department for Environment, Food and Rural Affairs (Defra) has said the problem has been caused by a combination of local emissions, light winds, pollution from the continent and dust blown over from Africa.

The comments from Cameron and Johnson infuriated MPs who have long been warning about air quality, and drew criticism from Labour, which accused the government of failing to get a grip on a serious public health problem.

Maria Eagle, the shadow environment secretary, said: "David Cameron is wrong to say our air quality crisis is due to just wind movement across continents.

"The real issue is that the government has no plan to address air pollution and has tried to hide the problem. They recently had to scrap their own air quality strategy because of evidence that it would have made the problem worse and they now have no plan at all.

"This is not just an environmental problem. It is a serious health problem because poor air quality causes 29,000 early deaths each year in the UK, at an average loss of life of 11.5 years."

Caroline Lucas, the Green party MP for Brighton Pavilion, said Cameron and Johnson were showing "appalling complacency". She urged the government to consider options such as asking people to use their cars less, rather than asking the sick and vulnerable to stay indoors. "There absolutely need to be more proactive measures taken by the government on this major public health issue," she said.People suffering breathing difficulties made thousands more calls to 999 than usual on Wednesday and Thursday in the smog-hit east of England and up into the west Midlands, while in London the ambulance service reported a 14% spike in calls for patients with respiratory problems.

A powerful band of Saharan dust loomed over east Anglia on Thursday night as showers were expected to bring some of the sand down and leave a rust-coloured layer across millions of cars and properties.

But experts said the eye of the dust cloud would be pushed away from Britain by strong Atlantic winds on Friday and Saturday, moving it towards Belgium, the Netherlands and north-west Germany.

"On Friday most parts of the UK will be in the low bracket for pollution so it's not anything we should be ridiculously worried about," said Laura Young of the Met Office. "By Saturday and the end of the weekend the whole country will be back to normal."

Forecasters at Defra said south-east Scotland, north-east England, north Wales and east Anglia would experience moderate levels of pollution – but far reduced from the record levels reached on Thursday.

Dr Matthew Loxham, of the University of Southampton, said: "While the combination of meteorological conditions and air pollution levels have brought about the current situation, we are more concerned about the general levels of air pollution that do not make the headlines.

"[General levels of air pollution] may affect the lung development of children and have as-yet uncharacterised effects on the health of those exposed to it. There is an even greater link between air pollution and effects on the cardiovascular system (eg heart disease and stroke)."