The embrace by central banks of low and negative interest rates pressures workers to bet on risky assets and could stifle consumer spending, the head of BlackRock warned Monday.

Larry Fink, chief executive of the New York-based investment giant, highlighted worries about rates in an annual letter to shareholders that called on governments to take a more aggressive approach toward the "retirement-savings crisis."

The European Central Bank, the Bank of Japan and others have adopted negative interest rates to spur growth, while the US Federal Reserve has maintained a policy of ultra-low rates, also seeking growth.

But Fink cautioned these policies are having unintended consequences.

"Not nearly enough attention has been paid to the toll these low rates -- and now negative rates -- are taking on the ability of investors to save and plan for the future," Fink said.

The drop in rates means that a 35-year-old looking to generate $48,000 a year of retirement income would need to invest today $563,00 with a rate under two percent, as compared with $178,000 at a rate of five percent.

"This reality has profound implications for economic growth: consumers saving for retirement need to reduce spending if they are going to reach their retirement income goals and retirees with lower incomes will need to cut consumption as well," Fink said.

"A monetary policy intended to spark growth, then, in fact, risks reducing consumer spending."

Fink said low rates are also creating "incentives to reach for yield, pushing investors into less-liquid asset classes and increased levels of risk, with potentially dangerous financial and economic consequences."

Fink's comments came ahead of the International Monetary Fund's annual spring meetings this week in Washington.

On Sunday, the IMF defended negative interest rates set by central banks, given "significant risks" of slow growth, while acknowledging potential for dangerous boom-and-bust cycles.

"Although the experience with negative nominal interest rates is limited, we tentatively conclude that overall they help deliver additional monetary stimulus and easier financial conditions," three top IMF officials wrote in a blog.

However, the IMF officials also said negative rates "may induce boom-and-bust cycles in asset prices," adding that "these potential risks require close monitoring and supervisory scrutiny."