Smoking should be banned from all London parks and other key outdoor public spaces, a new report by the Mayor’s London Health Commission has recommended.

The report, which will be presented by professor Lord Darzi to Mayor Boris Johnson today, also calls for new planning guidance to prevent “junk food” outlets from opening within 400 metres of schools, and a pilot scheme for a minimum 50p unit price for alcohol.

The smoke free plan would see the mayor use his byelaw powers over Trafalgar Square and Parliament Square, and his influence over the Royal Parks, the board of which he appoints. Local councils would pass similar byelaws for their parks and open spaces.

London has 20,000 acres of parks and open space, covering 40% of the city.

Lord Darzi said: “The ideas and proposals in this report have been developed for London. Yet they could just as easily apply to other big cities in the UK – London should be a leader, not an exception.”

“Hundreds of children take up smoking every week – two classrooms full a day – with advertising outlawed they do so inspired by the adults that they see. Once they start, they continue, since cigarettes are more powerfully addictive than narcotics. It’s little surprise that in places where more adults smoke, more children begin smoking too.”

The comission believes that the plan could reduce smoking prevalence in London from 18% to 16%.

Breach of the byelaws would be classed as a civil offence, with each authority able to set its own fine.

The commission estimates that it would cost £6.5m to implement over five years, including the cost of introducing new signage across parks and appointing compliance inspectors.