By Jonathan Cable

LONDON (Reuters) - The Bank of England will leave rates unchanged for another year and is coming to the end of a quantitative easing programme that economists say will prove to have been effective, according to a Reuters poll.

With interest rates at rock bottom, economists have switched all their attention to how much the central bank will spend on its quantitative easing programme, where it purchases government bonds from the market to expand the money supply.

The consensus from the poll, taken this week, predicted that the bank would eventually spend 150 billion pounds on the programme, in line with last month's estimate, having already spent 125 billion pounds.

"Events over the past couple of months justify an expansion of QE by a further 25 billion pounds to 150 billion pounds at the forthcoming meeting," said Philip Shaw at Investec.

Sixteen analysts saw the BoE extending the programme beyond the 150 billion sterling worth of purchases that the government has given permission for the central bank to make.

Retail sales have carried on falling and unemployment rising while the housing market, a bedrock of consumer wealth, is still languishing but a survey released earlier on Tuesday showed manufacturing output actually grew in June for the first time since last March.

Many of the forecasts were collected before revised figures showed the British economy shrank 2.4 percent -- its fastest pace in more than 50 years -- in the first three months of 2009.

Forecasts in the poll for the eventual total ranged between 125 billion and 350 billion pounds but 47 of 55 economists said the plan will ultimately be effective or very effective.