With all the talk of a possible double-dip recession in the U.S. economy—here’s my own little contribution—it’s surprising (and somewhat scandalous) that more attention isn’t being paid to what is happening in Britain, where a second economic downturn began last fall and shows few signs of relenting.

About a year ago, with the British economy seemingly recovering fairly well from the financial crisis of 2008, David Cameron’s Conservative-Liberal coalition embarked on a vigorous policy of deficit reduction, raising taxes and cutting government spending in an effort to balance the budget by 2015. How this experiment in pre-Keynesian economic policy turns out obviously has important implications for the fiscal debate on this side of the Atlantic.

So far, the results aren’t looking very favorable. In the four months from October to January, the U.K.’s G.D.P. actually fell. Since then, it has edged up slightly. According to a new report from the non-partisan National Institute for Economic Research, in London, in the three months to May the economy expanded, but by just 0.4 per cent—a miserly rate of growth.

Unlike other influential bodies, the N.I.E.S.R. hasn’t hesitated to label the current period as a “depression,” which it defines as a lengthy period in which an economy fails to surpass the previous peak in G.D.P. The economic downturn in the U.K. began more than three years ago, and G.D.P. is still about four per cent below the level it reached in early 2008. As the chart above shows, the current slump seems set to last at least as long as the downturns of 1930-1934, a.k.a. The Great Depression, and the savage “Thatcher Recession” of 1979 to 1983, during which large swaths of Britain were effectively de-industrialized.

The N.I.E.S.R. is not expecting output to pass its previous peak until 2013 at the earliest, and even this may well prove optimistic. The independent Office of Budget Responsibility, which the government set up last year to stop the Treasury from cooking the books, is forecasting growth of 1.7 per cent this year and 2.5 per cent in 2012. These figures might sound pretty modest, but with the government busy retrenching and consumers still digging themselves out of debt, they hinge on an upturn in exports and business investment that seems unlikely to materialize. Realistically, G.D.P. growth of one per cent this year and two per cent next year seems about the best that can be hoped for, and, absent a policy change, an even worse outcome can’t be ruled out.

Before my Conservative-leaning friends start howling (and yes, I do have some), I am not suggesting that the current recession is quite as deep or devastating as what befell the U.K. in the nineteen-thirties, or even the nineteen-eighties. The chart clearly shows that G.D.P. fell further in the nineteen-thirties. Compared to the nineteen-eighties, the current recession is slightly deeper in terms of G.D.P. What is very different this time is the pattern of unemployment. In the summer of 1932, the U.K. unemployment rate hit twenty-eight per cent, and in some depressed regions, such as Wales, it was considerably higher. Unemployment in the nineteen-eighties wasn’t nearly as bad, but the jobless rate did reach twelve percent, prompting outraged calls for a policy u-turn and eliciting Mrs. T’s most famous bon mot: “The lady’s not for turning.”

Currently, the British unemployment rate is 7.7 per cent, considerably lower than the rate in the U.S., but this number prompts many questions. During the past thirty years, U.K. governments from both parties have repeatedly massaged the official job figures. For example, many millions of able-bodied British adults are now classed as “disabled,” which enables them to claim disability benefits and disappear from the jobless rolls. A more meaningful measure of the labor and human potential going to waste is the fact that almost one in four Britons aged sixteen to sixty-four are now classed as “inactive” in the labor market.

Given this situation, you might think that concerned international bodies, such as the International Monetary Fund, would be urging Cameron and George Osborne, his whey-faced Chancellor, to consider adopting a Plan B. But there you would be wrong. Earlier this week, the I.M.F., after completing its annual inspection of the U.K. economy, issued a statement that looked suspiciously like it had been drafted in Downing Street.

“Aided by the implementation of a wide-ranging policy, the post-crisis repair of the U.K. economy is under way,” it began. “However, the weakness in economic growth and rise in inflation over the last several months was unexpected.”

Without pausing to answer the question of unexpected by whom—certainly not Lord Skidelsky and other Keynesian economists who warned all along that Osborne’s plan could well derail the British recovery—the I.M.F./Downing Street communiqué went on.

“This raises the question of whether it is time to adjust macroeconomic policies. The answer is no…. Strong fiscal consolidation is under way and remains essential to achieve a more sustainable budgetary position.”

And so, the great experiment continues, with sixty-two million Britons cast in the role of guinea pigs.