Sajid Javid vowed to make sure people caught up in the Windrush fiasco are treated with "decency and fairness" as he arrived at the Home Office to take up his new job.
Appointed Home Secretary after Amber Rudd quit following a turbulent week, Mr Javid said he would be looking "carefully" at the Government's immigration policy.
The former investment banker was given the job during a telephone call with Prime Minister Theresa May, who is on a local election campaign visit, and becomes the first person from an ethnic minority background to hold one of the four great offices of state.
He said: "The most urgent task I have is to help those British citizens that came from the Caribbean, the so-called Windrush generation, and make sure that they are treated with the decency and the fairness that they deserve."
He added: "We are going to have a strategy in place that does something the previous Home Secretary set out last week when she made a statement to Parliament about making sure we have an immigration policy that is fair, it treats people with respect and with decency.
"That will be one of my most urgent tasks, to make sure we look carefully at the policy and make sure it achieves just that."
He was replaced as Secretary of State for Housing, Communities and Local Government by former Northern Ireland secretary James Brokenshire, who has recently returned to Westminster after treatment for cancer.
International Development Secretary Penny Mordaunt takes on Ms Rudd's former responsibilities as Minister for Women and Equalities.
Ms Rudd resigned on Sunday after admitting she "inadvertently" misled MPs over Government targets for removing illegal migrants.
She had also been battling intense criticism over the Windrush scandal, which has seen people from a Caribbean background denied access to benefits and healthcare or threatened with deportation despite decades of residence in the UK.
She became the fifth enforced departure from the Cabinet since last year's snap general election and stepped down the evening before she was due to make a statement in the House of Commons.
Labour has made clear it does not believe that Ms Rudd's removal resolves the situation. Shadow home secretary Diane Abbott said that ultimate responsibility rests with Mrs May and called on the Prime Minister to come to the Commons to answer MPs' questions.
"All roads lead back to Theresa May and her tenure as Home Secretary," Ms Abbott told BBC1's Breakfast.
"Many of the elements of this hostile environment originated under Theresa May and, most important of all, it was in 2014 that she passed legislation which removed the protection from deportation which up until then had applied to Commonwealth citizens."
Mr Javid's appointment was welcomed by Cabinet colleagues. Culture Secretary Matt Hancock hailed him as "a serious political thinker who gets things done" while Chief Secretary to the Treasury Liz Truss described him as "effective, no-nonsense and brave".
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