The European Commission has said it is studying a proposal to impose value added tax (VAT) onsales of music, software and other "virtual" goods over the internet.
Mr Balls drew MPs' attention to previous U-turns on changes to the rules governing tax relief on charitable giving, and imposing VATon static caravan sales and hot takeaway food.
The shadow chancellor said he favoured a cut in VAT - which is a sales tax rather than a tax on income - because it would be the "fastest and fairest" way of boosting the economy.
Amazon is to be stripped of its huge tax advantage on the sales of electronic books after the European commission ordered Luxembourg to close a VAT loophole.