Tory grandees including have written to the prime minister warning that the government’s new borders bill will breach international law, going as far as to compare it with violations of international law by President Putin.

       A strongly-worded letter to Boris Johnson, signed by prominent Conservatives including David Davis and Dominic Grieve, states that the Nationality and Borders Bill be “dangerous” as it will see Britain “reinterpret” the 1951 Refugee Convention and “significantly breach key international obligations”.

       The bill, which is currently going through the House of Lords, will see the creation of a two-tier system for refugees in the UK depending on their method of arrival, with those who come via unauthorised routes – such as small boats or in the back of lorries – criminalised and penalised.

       With no UK resettlement scheme currently in place for Ukrainian nationals fleeing the Russian invasion, there is no safe and legal route for most of them to come to Britain, meaning they could fall into this category. The same is true for many Afghans fleeing persecution from the Taliban.

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       This approach is contrary to the Refugee Convention, which commits its 147 signatory-states to provide asylum to those genuinely fleeing persecution - focusing on why they came to the country, not the method by which they travelled.

       The letter states that the bill is “fundamentally at odds” with commitments made in the convention, which it points out was “based on the deadly lessons of the Holocaust”.

       “Ministers now suggest that the government understands the convention better than the UN itself, and that decisions on interpreting the convention can be left to parliament,” it continues.

       “We believe it will be dangerous if individual states seek to reinterpret internationally agreed treaties each according to their own wishes. You are right to condemn President Putin for breaking international law: it protects us all. That is true in other contexts, too.”

       The signatories, which also include former Labour home secretary Lord David Blunkett and former head of the diplomatic service Lord Kerr of Kinlochard, states that the “moral and legal underpinning is doubly important at a time when war is unfolding in Europe with incalculable consequences”.

       They go on to warn that the bill “threatens the integrity of the global asylum system” and that to go ahead with it in its present form would be “bad for refugees, bad for Britain and bad for the world”.

       The UN refugee agency, the UNHCR, has already warned that the news plans will stigmatise those seeking asylum in the UK as “unworthy and unwelcome”, creating a “lower class of status” for the majority of refugees, in violation of international law.

       Sonya Sceats, chief executive at Freedom from Torture, said: “The UN refugee agency, senior British jurists and political heavyweights have all warned that the Nationality and Borders Bill violates the Refugee Convention.

       “At a time when the Boris Johnson is chastising Putin for violating international law, it is unconscionable that he is pressing ahead with plans violate an international treaty that Britain helped draft.”

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       A Home Office spokesperson said: “The Nationality and Borders Bill, which has already been backed by MPs, will deliver the most comprehensive reform in decades to protect the vulnerable and ensure fairness in our asylum system.

       “This Bill reduces the incentives for people to make dangerous crossings and introduces a maximum sentence of life for evil people smugglers.”