Tony Blair and Gordon Brown made Labour electable in the 1990s by walking away from the class-warfare rhetoric of their party predecessors. Now Ed Miliband's Labourites want a moral crusade to raise taxes on the rich. Old Labour is back.

On Saturday shadow Chancellor Ed Balls promised to raise the top rate to 50% if Labour wins next year's election. Mr. Balls says it is "unfair" that the top 1% should pay any less and slams the Tories rate for what he calls "a huge tax cut for the richest people in the country."

Britain's Shadow Chancellor of the Exchequer Ed Balls. Reuters

The top rate reached the 50% mark at the end of Mr. Brown's premiership, amid a global financial panic and the sense that greedy bankers had caused all the trouble. David Cameron and Chancellor George Osborne spent their first two years in office foolishly defending the 50% rate, though they have since brought it down to 45%. But that's still up from the 40% top rate that held for most of the Blair-Brown tenure. A 40% rate is still high, but at least the system—with just two rates, 20% and 40%, toward the end—was simple and clear, unlike tax systems in France or the U.S.

If Mr. Balls had wanted to venture an intelligent criticism of the current system, he might have noted that the Cameron government has narrowed the tax base at the expense of the middle class. On the on hand, the government has dropped people from the tax rolls by raising the amount people need to earn to pay any tax at all to £10,000, up from £6,475 when Mr. Cameron took office. But this has been offset largely by subjecting more taxpayers to the 40% rate by lowering the income threshold at which it kicks in to £31,865 next year from £37,400 when the Tories came in.

Meanwhile, Britain's top 1% will pay 29.8% of all income taxes this year, up from 26.5% when Mr. Cameron came to power. In other words, British taxes have become more progressive under this government, even with a lower top marginal rate.

Such are the facts. Which means that the real message of Mr. Balls's pledge is that Labour is again seeking votes by appealing to class resentment rather than personal opportunity. The Conservatives' answer to Mr. Balls's proposal was to point out that raising taxes would hurt the economy and drive the rich abroad. Perhaps a cannier response would be to cut taxes to the Blair-Brown 40%-20% rates, and invite Mr. Balls to attack what used to be called New Labour.