Theresa May's mention of her response to the Grenfell Tower fire in her resignation speech has been described as "disgraceful" by the Fire Brigades Union.
The Prime Minister, who will step down on 7 June, mentioned the inquiry into the tragedy as she outlined how she used her premiership "to fight the burning injustices that still scar our society".
Matt Wrack, the Fire Brigades Union general secretary, issued a statement shortly after the speech on Friday, describing her response as "awful".
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Grenfell United, the campaign group, said residents were "devastatingly let down by the Government" and Justice4Grenfell also criticised Mrs May.
The fire in North Kensington, west London, on 14 June 2017 claimed the lives of 72 people.
An inquiry was launched in September that year, but is not expected to end until at least the end of 2021.
Kensington Labour MP Emma Dent Coad also issued a strongly-worded statement in which she said the Prime Minister should be "ashamed".
Mrs May said she "set up the independent inquiry into the tragedy at Grenfell Tower to search for the truth so nothing like it can ever happen again, and so the people who lost their lives that night are never forgotten".
Mr Wrack said: "Many of the underlying issues at Grenfell were due to unsafe conditions that had been allowed to fester under Tory governments and a council for which Theresa May bears ultimate responsibility.
"The inquiry she launched has kicked scrutiny of corporate and government interests into the long grass, denying families and survivors justice, while allowing business as usual to continue for the wealthy.
"For the outgoing prime minister to suggest that her awful response to Grenfell is a proud part of her legacy is, frankly, disgraceful."
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Emma Dent Coad said: "From the first day of her awkward visit to Grenfell, to her last day congratulating herself for failures, Theresa May should be ashamed of her actions and lack of leadership.
"Her predecessor's 'bonfire of red tape' was responsible for the decimation of building and fire safety regulations yet she did nothing to redress this."
Ms Dent Coad said the inquiry is "so narrowly focused that it threatens to exonerate the perpetrators of this avoidable atrocity and may not give any recommendations".
Grenfell United said the Prime Minister's "personal interventions have not delivered change".
A statement said: "It's hard to think of a greater injustice in recent years than Grenfell. We were devastatingly let down by the Government before, during and after the fire.
"We recognise that after her initial failings Theresa May has personally engaged with survivors and bereaved families, but two years later her personal interventions have not delivered change.
"The Government promised that 'no stone will be left unturned' in the fight for justice.
"Whoever becomes Prime Minister will inherit the moral debt owed by this Government to the families of 72 people who lost their lives."
The group said the Government has "failed" to deliver reform in response to the tragedy and "made the past two years a battle for survivors and bereaved".
A Justice4Grenfell spokesman said the group had "no evidence" Mrs May had made progress and criticised her failure to meet victims of the fire during her first visit to the scene.
A spokesman added: "Bereaved families, survivors and the affected community are losing trust in Mrs May's promised inquiry to search for the truth.
"She promised that all survivors would be housed within three weeks. There are still families living in emergency and temporary accommodation 23 months on."
The group said efforts to remove similar dangerous cladding from other buildings in the UK were "tardy", adding: "Nearly two years on, no recommendations or change to legislation has occurred to reduce the risk of additional preventable loss of life.
"Many continue to feel unsafe in their homes."