If Labor wins the next election it will use emergency powers to build new prisons and stop offenders being released months early due to overcrowding.

Shadow justice minister Shabana Mahmood said the prison was a “national emergency”.

Labor will use planning laws to stipulate that construction of new buildings must be completed “as a matter of urgency”.

Justice Secretary Alex Chalk said he was “very frustrated” that prison expansion was “bogged down” by the system.

He is also believed to have privately warned Rishi Sunak that prison places could run out within weeks.

Ms Mahmoud told the Sunday Times she would “achieve where the Conservatives failed and get to those 20,000 (extra places) as soon as possible” and no later than 2030.

She said: “For too long in this country we haven’t been able to build anything. This country needs to deliver these prison sites. I’m just not prepared to put public protection at risk further.”

Ms Mahmoud also said her plan would use the existing £4bn prison budget.

She added that the Conservatives could not claim to be the “natural party of law and order” but acknowledged that some people might “have an assumption about the way Labor does things. What I’m saying is that I’m interested in doing some cost-cutting crimes.” And keep people safe. I absolutely believe people need to be punished.”

She also spoke about the impact of the war in Gaza after Keir Starmer appeared to say on LBC radio that Israel had the right to cut off water and electricity from the besieged enclave.

“It leaves people feeling hurt, misunderstood, delegitimized,” she said. “I think the LBC interview and some of the other things about that period have led to a loss of trust between us and the British Muslim community and clearly we need to rectify that.” When asked if that could be rectified, she said: “I Think so,” even though it “wasn’t easy” and “people got hurt.”

In January, a former prison governor accused the government of announcing “panic” measures to tackle the prison capacity crisis.

Nick Hardwick, now a professor of criminal justice at Royal Holloway University, called for a radical rethink of prisoners being trapped in filthy, overcrowded cells 23 hours a day.

Last October, Alex Chalke announced a series of emergency proposals in response to the crisis, including the early release of some prisoners and plans to lease prison space overseas.

Mr Hardwick warned prison construction was not keeping pace with population growth.

In September it was revealed that plans to create 20,000 new prison places by the mid-2020s are not expected to be completed until 2030 due to planning delays.