WPP Martin Sorrell says tax 'a question of judgement'
Sir Martin Sorrell, chief executive of global advertising group WPP, has said the amount of corporation tax companies pay is largely "a question of judgement".
Sir Martin argued that companies like Google and Starbucks pay tax more out of a sense of corporate social responsibility, than because the law forces them to.
"Doing good is good business," he said.
WPP has now moved its headquarters back to London from Dublin.
Sir Martin spoke to the BBC's business correspondent Simon Jack.