Lawyers called for “adequate” coronavirus safety measures including “widespread testing” as they welcomed plans to open more Nightingale courts to help clear the rising backlog of criminal cases.

The first “super courtroom” to hear gang trials and more temporary courtrooms in hotels, theatres and conference centres are due to open, the Government said.

Manchester Crown Court will have a “super courtroom” to deal with cases involving several defendants on trial at the same time, such as gang murder trials.

The Ministry of Justice (MoJ) initially said 14 more venues were to be transformed into Nightingale courts, later clarifying that this would be 14 extra rooms in seven buildings in Aldersgate House in Barbican, London, the Manchester Hilton in Deansgate, and others in Birmingham, Croydon, Wolverhampton, Liverpool and Chichester – adding to more than 20 already open.

At the start of the year, the criminal courts backlog had risen again to over half a million, MoJ figures show, while some lawyers have said they are seeing trials being listed for 2023.

While opening more Nightingale courts showed “steps in the right direction”, Bar Council chairman Derek Sweeting warned: “These spaces need to be adequately staffed, testing needs to be widespread and justice needs greater financial support as a whole if we are to come out of this crisis with a system that can withstand knocks and deliver access to justice for the public.”

David Green, the president for the Law Society of England and Wales, said: “Swift further investment on a much greater scale is required to make inroads into the growing problem.

“If action is not taken to increase capacity further in a meaningful and safe manner, case delays will continue to increase and more and more victims, witnesses and defendants will be denied access to justice.”

Amy Shaffron, a senior associate at JMW Solicitors, said legal professions will take “some persuasion” that the courts will “actually be safe, as their previous efforts have not been up to scratch”, adding: “The courts continue to be a breeding ground for the spread of the virus.”

Meanwhile, Mayor of London Sadiq Khan accused the Government of “simply overlooking” the “serious pressures” London is facing by not setting up a super courtroom in the capital, saying it had been “disproportionately affected” by the backlog in cases.

It is thought more could be set up in future.

Last week the MoJ’s new permanent secretary Antonia Romeo said clearing the backlog was “very challenging”, telling MPs she cannot “pretend” it was not a “significant issue”.

There were 56,003 cases outstanding criminal cases in crown courts and 474,220 in magistrates’ courts as of January 24, according to the latest available MoJ figures.

This was more than 90,000 higher than the start of March last year before the country first went into lockdown.

Last month, Labour called for so-called “wartime juries”, cutting the size from 12 people to seven to help clear the backlog after justice watchdogs warned the “unprecedented and very serious” court case backlog poses the greatest threat to the criminal justice system in England and Wales.

Justice Secretary Robert Buckland previously said he hoped to clear the backlog of court cases exacerbated by the pandemic by Easter this year.

On Wednesday, he described the new courts as the “latest step” in “our battle to keep justice moving during the pandemic” and that an “immense amount” had already been achieved, adding: “I am determined to minimise delays and ensure justice is served for victims, defendants and the public.”

The Government has said it is investing £450 million to “boost recovery in the courts and deliver swifter justice”, insisting this is “already yielding results”.

More than 20,000 hearings using remote technology are now taking place each week – compared with around 550 in March 2020 – a 4,000% rise.