The families of five people killed in the Manchester Arena attack in 2017 have written to the prime minister, calling on him to ensure the new law will apply in the fullest way to MI5 and the other services.

The authors of the letter are the families of Liam Curry, 19, Chloe Rutherford, 17, both from South Shields, Megan Hurley, 15, from Liverpool, Eilidh MacLeod, 14, from the Isle of Barra, and Kelly Brewster, 32, from Sheffield.

In the letter, the bereaved families say: “You made a personal promise that you would bring in the law.

“We’re now asking you to keep that promise in full by ensuring the new law applies to the security and intelligence agencies in the same way it applies to everyone else.”

The letter adds: “MI5 failed our loved ones and failed us.

“It did so by failing to prevent the Arena bombing. But it then failed and hurt us further through its lack of candour after the attack.

“During the Manchester Arena inquiry, MI5 lied about the key intelligence it held about the suicide bomber before the attack.

“Despite MI5 lying to a public inquiry in this way, no one has been held to account.

“This lack of accountability needs to change. Creating a full duty of candour responsibility on MI5, MI6 and GCHQ is the clearest route to creating this change.

“We are dismayed that, as the draft bill is currently written, MI5 and the other organisations are being allowed to escape the full duty of candour responsibility.

“Every security and intelligence officer should be required the tell the truth, and the leaders of the organisations should also bear full responsibility.

“How many times must MI5 show that it cannot be trusted before something is done?

“We are calling on you to keep your promise and ensure that MI5, MI6 and GCHQ are held to the same standards as everyone else.”

Claire Booth, a sister of Kelly Brewster, survived the bombing and her daughter was severely injured. She told the BBC that MI5’s conduct after the attack was “infuriating” and made her feel like “we were collateral damage”.

She added: “It was just one of them things as far as MI5 were concerned.

“They didn’t stop it [the attack], but the fact that they’ve then not been truthful about what their involvements were, what they knew… it all just adds insult to injury. It’s not fair.”