HOME Secretary Priti Patel and minister without portfolio Nigel Adams have resigned from the Cabinet.
In a tweet, Ms Patel said she would continue "my public service to the country and the Witham constituency from the backbenches."
Ms Truss will announce her cabinet tomorrow night, and it is widely expected that Suella Braverman, the attorney general, will take over as home secretary.
In a letter to Boris Johnson, Ms Patel said "it has been the honour of my life to serve our country as home secretary for the last three years."
She also defended the government's controversial Rwanda policy, saying it was "vital" Ms Truss "backs all aspects of these policies on illegal immigration to ensure the full implementation and delivery of the new plan."
Ms Patel said the government's policies on immigration and crime "despite the relentless efforts of our political opponents and left wing activists, lawyers and campaigners who have sought to block these measures, regardless of what the majority of people in the UK want."
She added: "While they stand up for the criminals, terrorists, people smugglers, those with no rights in the UK, and people who threaten public safety and who do our country harm, we have never faltered and never stopped doing what is right to protect the public."
Ms Patel also promised to give Ms Truss her full support.
"It is my choice to continue my public service to the country and the Witham constituency from the back benches once Liz formally assumes office and a new home secretary is appointed," she added.
Mr Adams, an arch-Boris Johnson loyalist, said he was resigning as it was "important that a new prime minister is able to appoint a team based on who they want rather than who they inherit."
He added: "Since you announced your intention to stand down I have spoken to many constituents and it is clear to me that those who sought your demise do not understand the values and aspirations of those voters who put their trust in the Conservative Party for the first time in 2019."
His letter ended: "One thing for sure is that there has never been a dull moment along the way and I am honoured to call you my friend."