Tesco chief pays price of three poor years
Mr Lewis, who is president of personal care at Unilever and a non-executive director of BSkyB, will become the first ever outsider to run Tesco and will be tasked with turning around the ailing retailer.
Tesco shares rose 1.6pc in early trading on Monday, despite the retailer issuing a major profits warning alongside news of Mr Clarke's exit.
The company said that sales and trading profits in the first half of its financial year are "somewhat below expectations" due to tough trading conditions and the "increasing investments we are making to improve the customer offer and to build long term loyalty".
Mr Clarke has been chief executive of Tesco since 2011, but has overseen three years of declining sales since replacing Sir Terry Leahy.
Sir Richard Broadbent, Tesco's chairman, said Mr Clarke "agreed with the board that this is the appropriate moment to hand over to a new leader with fresh perspectives and a new profile".
Some leading shareholders and former directors have been pressing Tesco to change its management. Mr Lewis had earlier this year been touted as a replacement, with investors impressed by his focus on branding.