Labour mayor Andy Burnham said it is “frustrating” that the Government has failed to deliver on its promise to deliver a “Hillsborough Law” by the 36th anniversary of the disaster. The Greater Manchester Mayor and former Health Secretary said he “will not stop” until legislation to prevent future cover-ups is on the statute book.

Sir Keir Starmer promised at last year’s Labour conference that the proposed public office standards bill, known informally as the Hillsborough Bill, would be introduced before yesterday’s anniversary of the tragedy that cost 97 lives.

It would create a duty of candour for public servants including the police, and provide the families of victims with legal support to ensure they were properly represented at inquests or public inquiries.

Campaigners say the measures are essential after South Yorkshire Police and West Midlands Police paid damages for covering up the truth over the death of Liverpool fans in a crush at a 1989 FA Cup semi-final, while the legislation could also help the families of victims of the 1974 Birmingham pub bombings.

But the legislation has been delayed and a watered-down version is reportedly being prepared by the Cabinet Office.

Mr Burnham, who presented his own version of the law in a Private Member’s Bill in 2017, said: “It is now eight years since I presented the Hillsborough Law to Parliament and I find it frustrating that it has still not been enacted. Liverpool City Region Mayor Steve Rotheram and I made a solemn pledge to the families and survivors that we will not stop until we see it in full on the statute book, and we recommit the same to them today.

“It is too easy to cover up in this country and too hard for ordinary people to get to the truth. Reversing that reality is the single biggest thing we can now do in the names of the 97 people unlawfully killed that we remember on this day.”

Campaigners said they remained “in the dark” about the legislation on the 36th anniversary of the disaster. Speaking on ITV’s Good Morning Britain, Margaret Aspinall, whose son James died at Hillsborough aged 18, said: “I’m disappointed it’s not come out for the anniversary but at the same time I wouldn’t have accepted it being watered down because to me if it’s watered down it’s like giving me a jigsaw puzzle and there’s a couple of pieces missing.”

Ms Aspinall said: “If it’s not in all its entirety, I want nothing to do with it.”

The Prime Minister insisted he will deliver on the legislation, saying in a post on X: “Thirty-six years ago, we saw one of the greatest disasters in our history. A disaster that led to 97 people tragically losing their lives.

“Today, I pay tribute to them. In the years since, their families and loved ones have campaigned tirelessly to get justice. Despite all the challenges they have faced, they have kept fighting.

“I promised to bring a Hillsborough Law before Parliament, with a legal duty of candour for public authorities and public servants, and criminal sanctions for anyone who fails to comply. I will deliver on that promise.”

But Elkan Abrahamson, solicitor for Broudie Jackson Canter and director of the Hillsborough Law Now campaign, said: “We remain largely in the dark as to the status of the Bill and the next steps.”

Campaigners are planning to contact all MPs by the end of the month.