Mr Giordano will join British Gas immediately as a non-executive director, taking over as chairman after Robert Evans retires on 31 December.
Mr Evans announced his intention to retire at the company's annual meeting in April. The chief executive, Cedric Brown, remains in that post.
The new chairman - one of few British Gas executive directors to have come from outside the company - will have a salary of pounds 450,000 compared with Mr Evans's pounds 380,000. Unlike his predecessor, Mr Giordano will not receive share options or a bonus.
Mr Giordano is also non-executive deputy chairman of Grand Metropolitan and is a non-executive director of a number of companies, including Lucas. British Gas said that he would be spending most of his week with the gas company but would also remain with Grand Met. He will relinquish some other roles.
Mr Giordano joins British Gas at a crucial time. The Government is expected to respond within weeks to a report by the Monopolies and Mergers Commission which recommended that the company split off its trading arm and that full competition should be introduced into the domestic gas market in a decade.
Ministers have been lobbied by independent gas supply companies, including North Sea producers, which want to compete in domestic supply within a few years.
Mr Giordano said British Gas would need to focus on adding value for '2 million loyal shareholders and institutions'.Reuse content