The Bank of England surprised markets Thursday by sanctioning another 75 billion pounds ($116 billion) injection into a British economy that's suffering from the shockwaves of Europe's debt crisis and the British government's austerity program.

The Bank's rate-setting Monetary Policy Committee said it was reviving a program of asset purchases which injected 200 billion pounds in between March 2009 and January 2010 to help lift Britain out of a deep recession. The hope is that by buying government bonds from banks, they will use their cash injection to lend to hard-pressed businesses and households.

The scale of the asset purchases, which will take four months to complete, was more than anticipated by those predicting Thursday's move. Most economists thought the Bank would opt to wait until November before deciding on a more moderate 50 billion pound injection.

"It is clearly an indication of the extent to which the MPC is worried about the slowdown that it has chosen to act so soon and so decisively," said Peter Dixon, economist at Commerzbank.

In a statement, the nine members of the MPC said the pace of global expansion has slackened, especially in Britain's main export markets _ a reference to the eurozone, which is mired in a debt crisis that's beginning to impact on banks' day-to-day activities.

"Vulnerabilities associated with the indebtedness of some euro-area sovereigns and banks have resulted in severe strains in bank funding markets and financial markets more generally," the panel said. "These tensions in the world economy threaten the U.K. recovery."

Though the eurozone economy is also showing increasing signs of heading back into recession, the European Central Bank opted to keep its main interest rate unchanged at 1.5 percent. Many in the markets had been predicting a cut.

While launching another round of so-called quantitative easing, the Bank of England's panel left the base lending rate at an all-time low of 0.5 percent and said that inflation would likely undershoot the 2 percent target in the medium term in light of the deteriorating outlook. It's currently running at 4.5 percent and likely to go above 5 percent in the next month or two on the back of higher utility bills, the panel said.

"In the light of that shift in the balance of risks, and in order to keep inflation on track to meet the target over the medium term, the committee judged that it was necessary to inject further monetary stimulus into the economy," the panel said.

The pound slumped soon after the announcement, trading 1.1 percent lower at $1.5293 as investors were caught unawares by the surprisingly big increase.

Chris Williamson, chief economist at Markit, said the decision was not without risk but would bolster the economy "until European policymakers can find a resolution to the region's sovereign debt crisis and the U.K. government outlines a coherent strategy for growth."

The Bank acted a day after revised data showed that the British economy grew by only 0.1 percent in the second quarter, half the previous estimate. It managed little or no growth in the previous six months.

American economist Adam Posen has been alone among the nine Monetary Policy Committee members to vote last month for another 50 billion pounds in asset purchases, but minutes of that meeting signaled a shift in sentiment with "most members" agreeing that the case for more stimulus had strengthened.

With the base rate at an all-time low of 0.5 percent and the government cutting spending, quantitative easing is the only remaining big lever to jolt the economy to life.