Sir Keir Starmer has accused the Tories of using Brexit to deliberately run an “open borders experiment” in the UK.

The prime minister said the British people are “owed an explanation” after revised figures showed net migration reached a record high of almost one million under the previous government’s watch.

Follow live: Spending on asylum jumps to record high

Data from the Office for National Statistics (ONS) shows net migration for the year to June 2023 reached 906,000 – a big jump on what was previously thought and four times higher than pre-Brexit figures in 2019.

In a speech from Downing Street, Sir Keir said: “Failure on this scale isn’t just bad luck. It isn’t a global trend or taking your eye off the ball.

“No, this is a different order of failure. This happened by design, not accident.

“Policies were formed deliberately to liberalise immigration. Brexit was used for that purpose – to turn Britain into a one nation experiment in open borders.”

The ONS’s previous estimate for the year to 2023 was 740,000, which at the time was still a record amount.

The stats show net migration – the difference between people coming to live in and leaving the UK – is down 20% this year from the revised high of 2023, standing at an estimated 728,000.

Tory leader Kemi Badenoch yesterday admitted her party, which made repeated pledges to cut net migration by tens of thousands during their 14 years in office, had got immigration “wrong”.

But Sir Keir said their failures were “unforgivable” and can’t be separated from the Conservative Party’s “refusal to do the hard yards on skills, on welfare reform, on giving our young people opportunities”.

“Clearly the vast majority of people who entered this country did so to plug gaps in our workforce,” he added.

In his press conference, Sir Keir said Labour would reform the points-based immigration system to require companies that are heavily reliant on foreign workers to also train British people.

This will go alongside a crackdown on abuse of the visa system, including banning employers who flout the rules from hiring overseas staff for two years.

‘Landmark’ deal struck with Iraq

Sir Keir’s speech came as Home Secretary Yvette Cooper announced a “landmark” deal with Iraq, intended to crack down on the people smuggling fuelling illegal immigration.

Iraq is one of the top 10 countries people travelling in small boats come from (3,002 in the year to June). Around £300k of UK government money will be given to the country to help it with border security and law enforcement.

Home Office data released on Thursday also showed the cost of the UK’s asylum system has risen to £5bn, the highest level of spending on record, and up by more than a third in a year.

On Wednesday, Tory leader Ms Badenoch said there had been a “collective failure of political leaders from all parties over decades” to grasp migration, adding: “On behalf of the Conservative Party, it is right that I as the new leader accept responsibility and say truthfully, we got this wrong.”

Other Conservatives, including former home secretary Suella Braverman, sought to take credit for the numbers coming down in the year to July 2024, which the ONS said was driven mainly by a fall in the number of dependants arriving in the UK on study visas from outside the EU.