In November, the UK Supreme Court finally ruled that UK authorities' plans to deport undocumented migrants to Rwanda were unlawful. Sunak then announced his intention to introduce new "emergency legislation" so that plans to expel migrants could not be blocked again.
"It is with this mind that we fully appreciate that whilst our main wish is to strengthen the legislation, this means that in order to vote for amendments we will therefore need to offer you our resignations from our roles," the letter read.
The former lawmakers added that a system that "does not work in favor of the British people" had already derailed several bills.
The United Kingdom and Rwanda signed a migration agreement in 2022, under which people identified by the UK government as undocumented migrants or asylum seekers will be deported to Rwanda for processing, asylum and resettlement.
The plan has drawn criticism from human rights organizations and some politicians, who believe the measure will not help stem the flow of migrants. The first deportation of migrants from the UK to Rwanda was scheduled to take place on June 14, 2022. However, the flight was canceled at the last minute due to the European Court of Human Rights ruling.