Tens of thousands of Britons could be infected as a result of the contaminated blood scandal, the former judge leading an inquiry has suggested.

A public probe will consider the treatment of thousands of people in the 1970s and 1980s who were given blood products infected with hepatitis viruses and HIV, and the impact this has had.

Chairman of the inquiry, retired judge, Sir Brian Langstaff, addressed the hundreds of people who attended the start of the Infected Blood Inquiry in London on Monday.

“It is a truly sobering thought that if some of the claims are well-founded – and it is for this inquiry to find out if they are – there may yet be many thousands more who do not feel well, but have not yet been told that the reason for this is that they suffer from Hepatitis C,” he said.

Sir Brian said it is estimated that the number of infected could go far beyond 25,000 adding that there is a “real chance that these estimates may prove right”.

He added: “A sobering thought that the consequences of what was done then may be continuing to cause death even now.”

Victim Michelle Tolley spoke as the probe into the deaths of more than 2,400 people who were infected with HIV and Hepatitis C as a result of the scandal began.

“Anyone who may be responsible… they need to be held accountable and prosecuted if needs be – I strongly believe that,” the mother-of-four from Norfolk told the Press Association.

“People need to know that this tragedy happened,” she said. “This is the worst tragedy in the history of the NHS and it must never ever happen again, absolutely never.”

The 53-year-old was infected following a blood transfusion after the birth of her child in 1987 and another transfusion in 1991 – she eventually found out in 2015 that she had Hepatitis C.

Describing how she wakes up every day feeling as though she is “waiting to die”, she said she thought seeing the start of the inquiry would be a day that would never come, and worries she might not see it end.

Feeling “very positive” about the inquiry and that prosecutions could be achieved, she added: “I have great, great faith that they will leave no stone unturned.”

Sir Brian told those gathered that people will be at the heart of the inquiry, as well as ensuring it is properly funded, and independent of the Government.

He also revealed that the inquiry will be UK-wide and will not confine itself to London – with the aim to conduct hearings all over the country to enable more affected people to come in person.

And with allegations of a cover-up, which he said will be investigated, Sir Brian stressed that the probe will be as “open and transparent as it is legally possible to be”.

According to the terms of reference, which were published in July, the inquiry will consider “whether there have been attempts to conceal details of what happened” through the destruction of documents or withholding of information.

It will also consider if those attempts were deliberate and if “there has been a lack of openness or candour” in the response of the Government, NHS bodies and other officials to those affected.

During her opening statement, counsel to the inquiry Jenni Richards QC, said the terms of reference were a product of public consultation, describing it as a “moving, humbling, and enlightening process”.

“The inquiry does not underestimate the scale of the task which it faces,” she said. “It recognises that this is an immense undertaking which will require an enormous amount of work.”

Noting the breadth of issues and decades over which the scandal took place as another reason for the scale of the inquiry, she also cited the 100,000 documents already in the possession of the probe – a figure she said is likely to increase.

She also revealed that they intend for the inquiry to begin hearing evidence on April 30 next year, and how the aim is to sit three weeks out of every four, and up to four days a week.

Unable to give what she deemed a reliable answer as to how long the inquiry will take, Ms Richards confirmed that the process will not take less than a year and a quarter.

The inquiry will also likely hear from government ministers, she confirmed, with witness statements from senior politicians including successive secretaries of state for health, as well as senior civil servants and senior doctors involved in policy setting and decision making, set to be obtained.

“We anticipate that a number of such witnesses will be expected to give oral evidence, and thus be questioned publicly for the first time about their decisions and actions,” she said.

She said as an inquiry team they are “acutely aware” of how lives have been devastated and destroyed as a consequence of the use of infected blood products and infected blood.

“This inquiry cannot reverse or undo what has happened, but the inquiry team will do everything it reasonably can to provide the answers to the questions that have been sought for so long,” she added.

Prime Minister Theresa May announced in July last year that an inquiry would be held into the events over the two decades, when thousands of haemophiliacs and other patients in the UK were given infected blood products.

The announcement was welcomed at the time by campaigners, who have been pressing for years for an inquiry into the import of the clotting agent Factor VIII from the US.

Much of the plasma used to make the product came from donors such as prison inmates, who sold blood which turned out to be infected.

The inquiry continues on Tuesday.