The Bank of England's rate-setters have decided to pump another £50 billion of new money into the economy in their programme of quantitative easing.
It will take their total spending to £175 billion, unexpectedly going over the £150 billion set aside by the chancellor.
In a statement, they said that the recession in the United Kingdom "appears to have been deeper than previously thought".
The rate-setters also decided to keep interest rates unchanged at their historic low of 0.5% for a fifth month, the BBC reports.
There will now be increased focus on the Bank's latest economic projections, which will be published in the quarterly Inflation Report on 12 August.
The extra £50 billion will be spent over the next three months, which is a slower rate of spending than when the programme began in March.
The Bank of England has said it will have to expand the range of government debt it is prepared to buy.