Elizabeth Truss will today back Boris Johnson to the next prime minister, saying he can bring the country together.
The environment secretary, who campaigned for Britain to remain in the European Union, said talks with Brussels would need to be 'careful and tenacious'.
The former London mayor is set to stand with the support of Michael Gove.
Ms Truss and Mr Gove were both ministers in the Department for Education.
The South-West Norfolk MP said: 'The British people have sent a very clear message: they want change. I campaigned for the UK to remain but given the result, we now have a responsibility to get on with the process of leaving the European Union and doing what's right for Britain.
'We need strong leadership for this and that must now come from someone who campaigned to leave the European Union, who can bring the country together.
'That is just one reason why I am backing Boris Johnson.
'Boris was twice elected in London on a Conservative platform has just led a campaign which secured 17 million votes – the biggest endorsement in British electoral history.
'Our exit from the EU will require careful and tenacious negotiating and I am delighted Michael Gove will help Boris in this task. Michael gets results. With him on Boris's team, I am convinced we can get a good deal for Britain'.
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