img_3391-alan-clarke-Alan Clarke is UK economist at BNP Paribas. The opinions expressed are his own-

As expected, the Bank of England left the Bank Rate unchanged at 0.5 percent at the April meeting, the first unchanged decision since September 2008.

The accompanying statement was short and sweet. The Bank has accumulated 26 billion pounds of asset purchases and will take a further two months to complete the planned 75 billion pounds of purchases - see you next month!

It is disappointing that gilt yields haven't remained low - partly because of firmer economic data, but also because the market is wary of the exit strategy. Hence the statement was a bit of a missed opportunity. The Bank has run out of interest rate ammunition and hence is having to use alternative measures including quantitative easing. Some form of verbal intervention, voicing a desire to get gilt yields lower could have been a cheap and easy way to loosen conditions in the economy.

Ultimately we expect the scale and duration of quantitative easing to be more than most expect. Our models suggest that if the Bank Rate could fall below zero, interest rates "should" be -4 percent. That shows the magnitude of the stimulus that is required from unconventional policy. Given this, we expect Bank purchases of assets to amount to as much as double the 150 billion pound that the Bank is currently authorised to spend.

Quantitative easing is called unconventional policy for a reason. It is the last resort. We don't know if it will work; if it does work we don't know how well it will work or how quickly it will work; we don't know how big any side effects will be. If it was so fast and effective then it wouldn't be unconventional - we wouldn't bother moving the Bank Rate, we would use QE instead.