Former child refugee and Labor peer Alf Dubs said ministers would face opposition in the Lords over the plan unveiled by Home Secretary Priti Patel and Prime Minister Boris Johnson this week.
Lord Dubs said the Government was attempting to “ride roughshod” over international agreements.
He said: “I think it’s a way of getting rid of people the Government doesn’t want, dumping them in a distant African country, and they’ll have no chance of getting out of there again.
“I think it’s a breach of the 1951 Geneva conventions on refugees. You can’t just shunt them around like unwanted people.”
It comes as it was reported that Ms Patel took the rare step of issuing a ministerial direction to overrule concerns of civil servants about whether the concept will deliver value for money.
As part of the plan designed to curb migrants crossing the English Channel in small boats, those who are deemed to have entered Britain by unlawful means since January 1 may be sent to Rwanda where they will be permitted to apply for asylum in the African country.
According to reports, the claimed use of the ministerial direction by the Home Secretary was only the second deployment of the power within the Home Office in the past 30 years.
The Home Office declined to comment on the matter.
Speaking on Saturday, shadow prison minister Ellie Reeves said: “The UNHCR (UN Refugee Agency) has come out really, really strongly condemning the Government’s proposals, as have many organisations, and it seems the Government’s own civil servants have expressed huge misgivings about the plans, which seem to be completely misguided.”
The Labor politician said: “The Government is going to be paying £120 million upfront before any asylum seekers will be sent to Rwanda.
“Asylum seekers are saying it won’t stop them from crossing the Channel.
“We are in the middle of a cost-of-living crisis so it doesn’t seem the right way to be spending money on an unethical and unworkable scheme that won’t deter people from coming over.”
But Ms Patel said Denmark could be among those to reproduce the UK Government’s “blueprint”.
“There is no question now that the model we have put forward, I’m convinced is world class and a world first, and it will be used as a blueprint going forward, there’s no doubt about that,” Ms Patel said.
“I would not be surprised if other countries start coming to us directly on the back of this as well.”
The Home Secretary said Copenhagen was in talks with Rwanda as well, adding the Council of Europe “have also basically said they are interested in working with us”.
The Home Office denied its approach was in breach of refugee agreements. Lord Dubs, who came to the UK from then Czechoslovakia on one of the Kindertransport trains in 1939, said there would be legal challenges and opposition by peers.