The widow of PC Keith Palmer has said she is disappointed with the Metropolitan police after it emerged that she is suing the force over her husband’s murder by a terrorist attacker.

Palmer was stabbed to death as he guarded an entrance to the Palace of Westminster in March 2017. The Guardian understands Michelle Palmer’s legal action claims he might have survived had armed officers been stationed closer to the entrance. She is seeking damages for the loss of life and its effects on her and her young daughter.

The legal action repeats damning points raised during Palmer’s inquest and in an official report later by the then chief coroner. The report said the Carriage Gates, where the unarmed Palmer was stationed, were a known vulnerability. The inquest heard that armed officers were too far away, patrolling other areas of the Palace of Westminster’s grounds, amid confusion about their orders.

Michelle Palmer said on Tuesday she had wanted the legal action kept confidential and she was annoyed that the Met had publicly confirmed receipt of a letter from her solicitors at Slater and Gordon following media inquiries. The Met did not say whom the letter was from.

In a statement issued through her lawyers, Michelle Palmer said: “It was always of paramount importance that this matter remained private out of respect for me, my daughter and Keith. I am disappointed that the Met have made it public that a claim is being brought.

“Once more I feel disappointed and let down. This is not the respectful actions I, nor Keith, would have expected from an organisation that he dedicated his life to. It continues to feel as if our wishes are of little importance.”

The lawsuit is understood to be in its early stages. If it is not settled, it will be heard at the high court.

PC Palmer is regarded as a hero by rank and file officers, among others, and the Met’s leadership runs the risk of damaging its standing within the force the longer the legal action goes on.

Michelle Palmer’s solicitor, Patrick Maguire, said: “It has always been our position this matter proceed in confidence. It is with regret that the Metropolitan police have decided to publicly state that a claim is being intimated.”

Speaking after the October 2018 inquest, Palmer said of her husband: “He was left at a vulnerable location, with no protection, to die. The fact there were no firearms officers there for nearly an hour is hard to believe. I truly believe that if they had been there he would still be here today.”

Palmer, 48, was one of five people killed during an attack by Khalid Masood lasting 82 seconds on 22 March 2017.

Masood, 52, drove a vehicle into pedestrians on Westminster Bridge, killing four, before crashing into a barrier at the Palace of Westminster. He jumped out of the vehicle and ran towards the gates of parliament where he repeatedly slashed at Palmer, fatally wounding him.

Masood was shot dead by an armed officer guarding the then defence secretary, Michael Fallon.

The inquest’s conclusion criticised errors by the Met. “Due to shortcomings in the security system at New Palace Yard, including the supervision of those engaged in such duties, the armed officers were not aware of a requirement to remain in close proximity to the gates,” said the coroner, Mark Lucraft QC. “Had they been stationed there it is possible that they may have been able to prevent PC Palmer suffering fatal injuries.”

The Met said it would not be commenting further.