More than 70 terror attack survivors have demanded that all political parties agree a "charter" protecting their wellbeing after the election.
They want quicker access to mental health support and faster compensation.
The group, which includes survivors of the 2017 Manchester Arena bombing and attacks in London, also says all venues must set up anti-terror security plans.
Its demands follow Friday's London Bridge attack, in which two people were stabbed to death.
Jack Merritt, 25, and Saskia Jones, 23, are being honoured in a remembrance service at Guildhall Yard in the City of London on Monday.
Boris Johnson launched an urgent review after it emerged that convicted terrorist Usman Khan - who was shot dead by police following Friday's attack - had been released having served half his sentence.
The prime minister blamed legislation introduced when Labour was in power and said there were currently 74 people convicted of terrorist offences who had been released early.
But Labour leader Jeremy Corbyn accused the Conservatives of trying to keep people safe "on the cheap" and called for more funding for public services, including probation and mental health.
Its letter says: "We are sick of the promises [made by politicians] that never materialise. The promises to look after victims who then face months of delay for mental health support or years of waiting for compensation.
"We ask all of the parties to agree to consult on and implement a new 'Survivors' Charter' that would guarantee basic rights and services for survivors."
The group wants MPs to back "Martyn's Law", compelling all owners of events spaces to have in place a "basic security plan". This is named after Martyn Hett, killed in the Manchester Arena bombing in May 2017, in which 22 people were killed.
The group says it is "sick of promises that never materialise" but praises the "heroes" who confronted Khan on London Bridge, preventing him from continuing his attack.
It also asks the public not to "give the terrorists what they want by sharing videos or views from attackers or by blaming whole groups or giving in to hate".
And it wants the media to "allow survivors the space to recover after terrorist incidents and to focus coverage on the heroes rather than the attackers".
Three people were injured in Friday's attack, which Khan began at a prisoner rehabilitation conference, organised by Cambridge University, at Fishmongers' Hall, next to London Bridge.
Two of the injured remain in hospital and are described as being in a stable condition.