The activist economic policies adopted by governments since the financial crisis have had mixed results, according to a group of Citigroup analysts led by William Lee, managing director of the global chief economist team.

"Monetary, fiscal and regulatory policymakers globally have had to discard historical practices and become more discretionary, politically contentious and interventionist," they write in a commentary obtained by CNBC.

"On net, these policy developments collectively have heightened global uncertainty even as the recovery muddles along."

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Investment has been weak since the financial crisis, the analysts say. That's "because of the dizzying array of unusually active policy measures implemented in the United States and the anxiety-provoking anticipation of reform measures in Europe since the crisis," they explain.

"With growing uncertainty about the outcome of these unprecedented policy changes, investment plans were delayed or cancelled, and aggregate demand faltered. Indeed, it is time to amend the old maxim that the path to Hell is lined with good intentions and unintended consequences."

To boost investment, policymakers may do better to do less, or at least be more predictable, the analysts say.

Jeremy Warner of The Telegraph says that central banks aren't accomplishing much. "More or less everywhere, from Britain to America and Japan, and from Nigeria to India and Europe, central bankers have become the first, second, third and last line of defense for almost every economic problem that arises," he writes.

"In the end, central banks can offer no more than sticking-plaster solutions, yet both the power and the expectation vested in them grows by the day."

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