Lamb's predecessor Edward Davey has moved to the role of energy secretary, following Chris Huhne's resignation this morning.
Business Secretary, Vince Cable said: "I am delighted to welcome Norman Lamb to the Department. Norman's professional background as an employment lawyer and experience as the Liberal Democrat's Trade and Industry Spokesman make him an ideal replacement.
"Norman pioneered our policy to privatise Royal Mail and establish employee share ownership in the business so it is fitting that he will be responsible for implementing that policy.
"I wish Edward Davey well in his new Cabinet role. He has made a fantastic contribution to the Business Department's work; successfully steering the Postal Services Act through Parliament to secure the future of Royal Mail, formulating the proposals to introduce a system of shared parental leave and negotiating the first small business exemption in European regulation, to name but a handful of his achievements."
Lamb added: "I'm honoured to be joining a department which is doing such an incredibly important job delivering the jobs and growth Britain needs. In particular, I'm pleased to be implementing the Royal Mail reforms I pioneered in opposition and giving employees a stake in the company.
"Edward Davey has been an immensely impressive minister and I look forward to picking up where he left off. And I am thrilled to be working alongside my friend and colleague Vince Cable who is doing excellent work to get Britain back on its feet."
Lamb has been an MP for North Norfolk since 2001. Before he entered Parliament he was a partner at law firm Steeles Law where he was the head of the firm's specialist Employment Unit.
