Boris Johnson has vowed to urgently relax stop and search restrictions for police officers across the UK, in a controversial first full policy announcement as prime minister.

Downing Street said that a trial scheme designed to make it easier for officers to conduct searches would be “urgently” reviewed, with a view to extending it across the whole country.

Mr Johnson also vowed to begin the process of recruiting 20,000 new police officers within “weeks”, saying the Home Office would launch the recruitment drive in September.

The stop and search trial began in April and involved seven police forces following less strict conditions in relation to searches.

Mr Johnson has repeatedly said that he supports stop and search being used to tackle violent crime. Critics say the controversial policy disproportionately targets ethnic minorities and is frequently used without good reason.

As the then Mayor of London, Mr Johnson said in 2016 that he was “concerned” at the high number of searches being carried out and called for “a more targetted approach”.

However, during the Tory leadership campaign this summer he said he wanted to give the police “the political cover and support they need to do stop and search and to come down hard on those carrying knives”.

He also pledged to recruit 20,000 new police officers within the next three years.

Downing Street said the government would set up a new national policing board to help drive the recruitment process. It will be chaired by Priti Patel, the new home secretary, and will bring together police leaders to ensure forces are doing all they can to recruit new officers.

Mr Johnson said: “As I said on the steps of Downing Street this week, my job as prime minister is to make our streets safer.

“People want to see more officers in their neighbourhoods, protecting the public and cutting crime.

“I promised 20,000 extra officers and that recruitment will now start in earnest.”

Boris Johnson's cabinet: Who's in and who's out Show all 40 1 /40 Boris Johnson's cabinet: Who's in and who's out Boris Johnson's cabinet: Who's in and who's out In: Jacob Rees-Mogg Jacob Rees Mogg appointed Leader of the Commons AFP/Getty Boris Johnson's cabinet: Who's in and who's out In: Esther McVey Esther McVey appointed housing secretary AFP/Getty Boris Johnson's cabinet: Who's in and who's out In: Jo Johnson Jo Johnson appointed new business and energy secretary EPA Boris Johnson's cabinet: Who's in and who's out In: Brandon Lewis Brandon Lewis appointed immigration secretary Getty Boris Johnson's cabinet: Who's in and who's out In: James Cleverly James Cleverly appointed Conservative Party chairman PA Boris Johnson's cabinet: Who's in and who's out In: Baroness Evans Baroness Evans remains Leader of Lords PA Boris Johnson's cabinet: Who's in and who's out In: Julian Smith Julian Smith appointed Northern Irish secretary Reuters Boris Johnson's cabinet: Who's in and who's out In: Alister Jack Alister jack appointed Scottish secretary PA Boris Johnson's cabinet: Who's in and who's out In: Alun Cairns Alun Cairns remains Welsh secretary AFP/Getty Boris Johnson's cabinet: Who's in and who's out In: Grant Shapps Grant Shapps appointed transport secretary Getty Boris Johnson's cabinet: Who's in and who's out In: Alok Sharma Alok Sharma appointed international development secretary AFP/Getty Boris Johnson's cabinet: Who's in and who's out In: Robert Buckland Robert Buckland appointed justice secretary Getty Boris Johnson's cabinet: Who's in and who's out In: Amber Rudd Amber Rudd remains work and pensions secretary Getty Boris Johnson's cabinet: Who's in and who's out In: Robert Jenrick Robert Jenrick appointed housing and communities secretary AFP/Getty Boris Johnson's cabinet: Who's in and who's out In: Andrea Leadsom Andrea Leadsom appointed business secretary Reuters Boris Johnson's cabinet: Who's in and who's out In: Nicky Morgan Nicky Morgan appointed culture secretary Getty Boris Johnson's cabinet: Who's in and who's out In: Gavin Williamson Gavin Williamson appointed education secretary AFP/Getty Boris Johnson's cabinet: Who's in and who's out In: Theresa Villiers Theresa Villiers appointed environment secretary AFP/Getty Boris Johnson's cabinet: Who's in and who's out In: Liz Truss Liz Truss is appointed international trade secretary Reuters Boris Johnson's cabinet: Who's in and who's out In: Ben Wallace Ben Wallace appointed defence secretary EPA Boris Johnson's cabinet: Who's in and who's out In: Stephen Barclay Stephen Barclay remains EU secretary AFP/Getty Boris Johnson's cabinet: Who's in and who's out In: Dominic Raab Dominic Raab appointed foreign secretary AFP/Getty Boris Johnson's cabinet: Who's in and who's out In: Priti Patel Priti Patel appointed home secretary AFP/Getty Boris Johnson's cabinet: Who's in and who's out In: Michael Gove Michael Gove given Chandellor of the Duchy of Lancaster AFP Boris Johnson's cabinet: Who's in and who's out In: Sajid Javid Sajid Javid is appointed Chancellor of the Exchequer AP Boris Johnson's cabinet: Who's in and who's out Out: Jeremy Hunt Jeremy Hunt sacked as foreign secretary Reuters Boris Johnson's cabinet: Who's in and who's out In: Matt Hancock Matt Hancock remains health secretary AFP/Getty Boris Johnson's cabinet: Who's in and who's out Out: Chris Grayling Chris Grayling resigned as transport secretary Getty Boris Johnson's cabinet: Who's in and who's out Out: Jeremy Wright Jeremy Wright sacked as culture secretary PA Boris Johnson's cabinet: Who's in and who's out Out: Karen Bradley Karen Bradley sacked as Northern Ireland secretary Getty Boris Johnson's cabinet: Who's in and who's out Out: James Brokenshire James Brokenshire sacked as housing and communities secretary Reuters Boris Johnson's cabinet: Who's in and who's out Out: Penny Mordaunt Penny Mourdaunt sacked as defence secretary Reuters Boris Johnson's cabinet: Who's in and who's out Out: Liam Fox Liam Fox sacked as international trade secretary Getty Boris Johnson's cabinet: Who's in and who's out Out: Greg Clarke Greg Clarke sacked as business secretary PA Boris Johnson's cabinet: Who's in and who's out Out: David Mundell David Mundell sacked as Scottish secretary Getty Boris Johnson's cabinet: Who's in and who's out Out: Damien Hinds Damien Hinds sacked as education secretary Getty Boris Johnson's cabinet: Who's in and who's out Out: David Gauke David Gauke resigned as justice secretary EPA Boris Johnson's cabinet: Who's in and who's out Out: Rory Stewart Rory Stewart resigned as international development secretary Getty Boris Johnson's cabinet: Who's in and who's out Out: David Lidlington David Lidlington resigned as deputy Prime Minister PA Boris Johnson's cabinet: Who's in and who's out Out: Philip Hammond Philip Hammond resigned as Chancellor of the Exchequer AFP/Getty

Ms Patel said: “Officers up and down the country put themselves in danger every day to keep us safe, they deserve our support.

“The rise we’ve seen in serious violence is deeply worrying. An additional 20,000 officers sends a clear message that we are committed to giving police the resources they need to tackle the scourge of crime.”

The home secretary said the announcement marked “the start of a new relationship between the government and the police working even more closely together to protect the public”.

Speaking in the Commons earlier in the day, Mr Johnson said he had told Ms Patel to treat the work of recruiting more police officers as “an absolute priority”.

He also hinted at the changes to stop and search rules, saying: “We will give greater powers for the police to use stop and search to help tackle violent crime.”

Mr Johnson said he had asked civil servants to draw up plans for tougher penalties for people found guilty of serious sexual and violent crimes, including ensuring that they serve time in prison. This will be accompanied by policies to reduce the number of “prolific offenders”, he said.