Several women, wearing red evening dresses and sashes with the words 'climate emergency', prevented Hammond from speaking for a few minutes by using loudspeakers to shout slogans during a banquet in London's landmark Mansion House building.
Big internet companies, which say they follow tax rules, had previously paid little tax in Europe, typically by channelling sales via countries such as Ireland and Luxembourg which have light-touch tax regimes.
Hammond infuriated pro-Brexit newspapers this week and was criticised by some Conservatives including former finance minister Nigel Lawson for not agreeing to spend money now on preparations for the possibility of Britain leaving the EU without a deal.
Philip Hammond's words echo those of May, who last week issued her own defence of capitalism - a sign of growing concern about the threat Labour poses to the pro-business orthodoxy that has underpinned British economic policy since Margaret Thatcher's reforms in the 1980s.
Philip Hammond, who campaigned for Britain to stay in the EU in last year's referendum but now supports withdrawal, is seen as an advocate of a more moderate "soft Brexit" in contrast to more hardline ministers.