The home secretary has rejected calls from the family of MP Sir David Amess for a public inquiry into his murder.

In a letter addressed to Lady Julia Amess and Katie Amess, Yvette Cooper said it was “hard to see how an inquiry would be able to go beyond” killer Ali Harbi Ali’s trial and recently published Prevent learning review.

Katie Amess, daughter of Sir David, said Cooper’s words were “adding salt on to an open wound”, branding them “unacceptable” and “insulting”.

Sir David, the Conservative MP for Southend West, was stabbed to death by Ali, a fanatic of so-called Islamic State, at a constituency surgery on 15 October 2021.

His widow, Lady Amess, said Sir Keir Starmer should “go away and reconsider the government’s position” ahead of the family’s meeting with the prime minister and the home secretary on Wednesday.

Describing her reaction to the letter, Katie Amess said she felt “sadness, betrayal, pain and just heartbreak, really”.

Sir David’s family called on the prime minister to consider including his murder in the public inquiry into the Southport killings.

Ali had been referred to Prevent seven years before he fatally stabbed Sir David 20 times at Belfairs Methodist Church in Leigh-on-Sea.

He was sentenced to a whole-life order at the Old Bailey in 2022, having been found guilty of murder and preparing acts of terrorism.

Sir David’s family received a letter rejecting their call for a public inquiry into the case on Thursday, details of which were made public on Monday.

In her letter, Cooper said a coroner had already “looked carefully” at whether to resume an inquest into Sir David’s death following the criminal trial.

She wrote: “[But] they concluded there were no additional questions that could be answered through an investigation of this kind, that had not already been considered as part of the trial.

“In the circumstances it is therefore hard to see how an inquiry would be able to go beyond what has been reviewed in the trial, Prevent learning review, coroner’s report, as well as Lord Anderson and Essex Police’s forthcoming conclusions.

“On that basis, the government cannot establish a public inquiry.”

The home secretary told the Amess family she had decided to “appoint an independent external reviewer to look across the findings of the investigative work and scrutiny already completed or under way”.

She continued: “I realise this is not the answer you were looking for.

“I remain keen to discuss this with you in the forthcoming meeting with the prime minister.”

Lady Amess said the government should reconsider its position for the “security of all public servants, and for every citizen who deserves to know when the state fails”.

She said: “Despite our repeated calls, we have been denied the one thing that can provide real answers – a full public inquiry.

“To pour salt on the wound, Yvette Cooper has now written us a totally unacceptable and, quite frankly, insulting letter, confirming that the government will not order an inquiry, and that all the investigations to date should satisfy us.

“Well, I can tell her they most certainly do not.”