Number 10 has announced that secretary for work and pensions Iain Duncan Smith will remain in post after the cabinet reshuffle.
Employment minister Chris Grayling has been appointed as justice secretary, replacing conservative stalwart Ken Clarke.
No news has yet emerged on whether pensions minister Steve Webb will continue in his role.
The decision was taken to keep Duncan Smith in place because David Cameron wants "strong reformers" to continue their work, the BBC reports.
There were rumours that Duncan Smith, who has presided over the Department for Work and Pensions during a period of unprecedented reform of welfare and pensions, had been offered the role of justice secretary but turned it down.
Cameron has announced he will also keep education secretary Michael Gove and chancellor George Osborne in post, despite controversy over their reforms.
There have been no announcements yet concerning Maria Miller, minister for disabled people, Steve Webb, pensions minister, or Lord Freud, minister for welfare reform.
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