Downing Street offered its support for the “important work” of the Covid inquiry following reports that its cost could reach £145 million.

Official documents released by the UK Covid-19 Inquiry have stated that the review into the pandemic has cost £56 million, as of September 30.

According to analysis by LBC of awarded government contracts, the inquiry’s bill could rise by almost a further £90 million.

The Prime Minister’s official spokesman said the chair of the independent inquiry, Baroness Heather Hallett, could take decisions “as she sees fit” as long as they are within the agreed terms of reference.

It is right that an independent chair is able, within the terms of reference that are agreed by the former prime minister, to act independently and take decisions as she sees fit

LBC reported that solicitor and legal contracts in the Covid inquiry are scheduled to total more than £50 million by the end of 2026.

If correct, the £145 million cost would make the investigation into the coronavirus pandemic one of the most expensive in recent British history.

Government data shows the Bloody Sunday Inquiry, held between 1998 and 2010, cost £191 million, while the probe into Harold Shipman’s murders cost £21 million.

The fact-checking organisation FullFact said almost £100 million of the costs during the inquiry into the events in 1972 in Londonderry, when members of the Parachute Regiment shot dead 13 civil rights protesters on the streets of the city in Northern Ireland, went on legal representation.

Asked by reporters whether Rishi Sunak regarded the inquiry as representing value for money, the Prime Minister’s spokesman said on Thursday: “The Government established the inquiry.

“We wanted to focus on its core objectives to ensure we have learned lessons and are best prepared to deal with any future pandemics.

“That is important work. We will continue to co-operate with it.”

Asked whether the inquiry had been set a budget, the No 10 official said he did not know the “latest” about its funding.

The spokesman added: “They are independent.

“It is right that an independent chair is able to, within the terms of reference that were agreed by the former prime minister, to act independently and take decisions as she sees fit.

“Obviously, the important point being that they need to be in line with the terms of reference.”

A spokesman for the inquiry, in a statement to LBC, said: “The inquiry chair, Baroness Hallett, set out in her opening statement the substantial task faced by the inquiry to consider and report on the preparations and the response to the pandemic in England, Scotland, Wales and Northern Ireland.

“She made clear that to do this properly will take time and have a significant cost.

“The inquiry regularly publishes its financial information and we have rigorous governance processes in place to make sure we are delivering value for money when fulfilling the inquiry’s terms of reference.”

The inquiry has been contacted by the PA news agency.

Mr Sunak gave evidence before Lady Hallett on Monday during a hearing in which he defended the Eat Out To Help Out hospitality discount scheme that he supported when chancellor in the summer of 2020.

The Conservative Party leader faced criticism from MPs and bereaved families after he said changing phone multiple times since the outset of the coronavirus crisis meant he could not provide his WhatsApp messages relating to the pandemic to the inquiry.

He also said he could not remember a number of key details, including the Cabinet meeting chaired by former premier Boris Johnson at which the first lockdown in England was agreed in March 2020.