The Council of Europe has told the British government that plans to end prosecutions in cases related to the Troubles in Northern Ireland risk "undermining human rights protection and would cut off avenues to justice for victims and their families".
In a letter to the Northern Ireland Secretary Brandon Lewis, Commissioner for Human Rights Dunja Mijatovic said if adopted, the plan would "lead to impunity and cannot be the foundation on which transitional justice is built".
Instead, the European Human Rights and Democracy body said the UK government should focus on "delivering justice across all communities without further delay", as a way of dealing with the so-called legacy issues.
Replying to the criticism, Mr Lewis said the British government was committed to dealing with legacy issues in ways that comply with human rights obligations, and said the proposals published in July were a consultation paper, not a final position.
The British government proposal introduces a statute of limitations for all Troubles-related crimes, accompanied by a statutory bar on investigations by the Police Service of Northern Ireland and Police Ombudsman.
It also ends all judicial activity with regard to criminal and civil cases and inquests.
Instead, it will introduce an information recovery body.
The Human Rights Commissioner said this proposal would fall short of the UK's obligations under the European Convention on Human Rights to carry out effective investigations into serious human rights violations.
It said the proposal amounts to "a broad-based and unconditional amnesty, including for killings and torture", and the move "effectively means that none of those involved in any serious violations will be held to account".
The commissioner said that the justification for the proposed approach is based on a "false dichotomy" between investigations and prosecutions on the one hand, and truth and reconciliation on the other.
The commissioner points out that impunity and the absence of justice can be a major impediment to achieving lasting peace and reconciliation, including by undermining incentives to participate in truth seeking and the trust necessary for truth and reconciliation efforts to be effective.
"The people of Northern Ireland have waited far too long for progress in dealing with legacy issues", she said.
By shifting away from previously agreed approaches, rather than implementing them, the current proposals are likely to only delay progress in this area.
The commissioner called for further reflection on the responsibility of the UK government in creating the long-standing delays in delivering on promises regarding legacy issues.
She also raised concerns about the lack of a victim-centred approach and noted that the pursuit of justice, including through investigations and prosecutions, is central to the efforts of many victims and their families in coming to terms with the past, with the prospect of facing more delays or an abrupt end to their search for justice clearly being devastating for them.
"Taking the option of investigations and prosecutions off the table unilaterally undoubtedly fails to meet the wishes of a significant group of victims", she wrote in the letter.
Mr Lewis said: "The UK government is committed to dealing with legacy issues in a way that supports information recovery and reconciliation, complies with international human rights obligations, and responds to the needs of individual victims and survivors, as well as society as a whole.
"In publishing our proposals for addressing the legacy of Northern Ireland's past in the Command Paper of 14 July, we were clear that these were intended not to represent a final position but rather to inform a process of engagement.
"This engagement - which involves meeting with political representatives, representatives from the victims sector and victims and survivors directly - is ongoing and we are listening to and considering the views we are hearing very carefully as we reflect on the way forward."
The Council of Europe has 47 member states, and is entirely separate from the European Union. The UK is still a member of the Council of Europe, and is a signatory of the European Convention on Human Rights.