Milton Friedman, who has died aged 94, was not the most important economist of the post-war era - that title belongs to the brilliant Paul Samuelson - but he was certainly the most controversial. Yet despite his views being championed by so many politicians on the right, it may come as a surprise that Friedman's career as a policymaker largely ended in failure.

Given his status as a long-standing hate figure, the assumption by many of the left is that his agenda was cemented into place during the Reagan and Thatcher administrations in the early 1980s, especially Friedman's well-known view that inflation is solely influenced by changes in the money supply. But very few of Friedman's most cherished proposals were ever put in to practice. Of those that where - such as monetarism - almost all turned into failure.

The great irony for Friedman's fans is that the one piece of public policy he was responsible for that was widely and internationally adopted was one that greatly increased the ability of central governments to collect taxes - a policy he later repudiated in disgust.

Obituaries of Friedman will doubtlessly sing of his successes. But close examination will show them to be few, and none unalloyed. For all his high public profile - thanks to his regular column in Newsweek and series on US television, Free To Choose, which made him into something of a star - today no mainstream academic economist is a monetarist and Friedman left no lasting school of academic heirs. Even the "Chicago school" at the University of Chicago has waned in influence, eclipsed by the mighty MIT army of economists that followed Samuelson.

Of course Friedman is greatly respected for his theoretical work as an economist, especially on his analysis of the role of money, the importance of inflation expectations in wages and employment, and perhaps his most lasting contribution (it could be argued), the permanent income hypothesis, which suggests that households take a longer view of anticipating their past and future income than previously thought. His award of a Nobel prize in economics was richly deserved - even if he was churlish in accepting it (he said after winning: "I would not want a professional judgment of my scientific work to be those seven people who selected me for the award").

In terms of the policies he inspired or influenced, however, the report card is not so glowing. His great claim, the idea that "inflation is always and everywhere a monetary phenomenon" may have set off the Monetarist versus Keynesian "econ-wars" of the late 1970s and 1980s. But Friedman's ideas of directly targeting the money supply were tried and rejected as a failure, in both the UK and the US, and Friedman himself backed away from his dogmatic earlier positions. Today, no major central bank directly targets money supply data in setting monetary policy - instead they are far more pragmatic. Even Friedman's great admirer Alan Greenspan never tied himself to the monetarist mast, preferring to keep his options open.

Friedman also railed long and hard for school vouchers to be adopted, to little avail, and his libertarian leanings provoked him to call for recreational drugs and prostitution to be legalised. He lobbied against environmental protection and regulations of all kinds, the vast majority of which were happily ignored by his friends and enemies. Even the economic reforms in Pinochet's Chile he is said to have inspired have run into trouble.

Friedman's first big role as a policy advisor came in 1964 to Barry Goldwater - the least successful Republican presidential candidate in the last 100 years. His next gig was for Richard Nixon - an unsuccessful president in a different way - although Nixon ignored him when it mattered, except when he could use Friedman as cover for politically difficult decisions, such as ending compulsory military service.

And Friedman's one success? In 1942, during world war two, Friedman actually went to work for the US government. While there he helped design the payroll tax that in Britain is known as PAYE, Pay As You Earn, and in the US as withholding tax, the system that allows the government to administer the taking of income tax directly from salaries and pay packets. Unlike everything else he argued for, withholding tax was withstood the test of time and is in use all around the world. It was the best thing that Keynesian-style government could ever have wished for, and Friedman bitterly regretted it. In his memoirs he wrote:

"It never occurred to me at the time that I was helping to develop machinery that would make possible a government that I would come to criticize severely as too large, too intrusive, too destructive of freedom. Yet, that is precisely what I was doing. [My wife] Rose has repeatedly chided me over the years about the role that I played in making possible the current overgrown government we both criticize so strongly."

Rest in peace Milton Friedman, big government's best friend.