The UK is going through a "slow and difficult healing process” as it rebalances its economy, the prime minister has said.It comes as the International Monetary Fund (IMF) downgraded its growth forecast for the UK, which it now expects to shrink by 0.4% this year.Mr Cameron said the government was doing "everything it can” to encourage growth in difficult economic times.And the government has cut the budget deficit by a quarter in two years.According to the IMF the prospects for the global economic recovery are weakening as government policies have failed to restore confidence.It has downgraded its overall estimate for global growth, with one of the biggest country downgrades applied to the UK.The IMF now expects the British economy to shrink by 0.4% this year, compared with its forecast of 0.2% growth in July. David Cameron, who is in Birmingham for his party’s annual conference, defended his government’s economic strategy and said there were "positive signs” the UK economy was changing.Speaking on BBC Radio 4’s Today Programme, he said: "What is happening in Britain is a rebalancing of our economy. "We need more private sector growth, we need a smaller public sector, we need to make more, sell more overseas and manufacture more."It’s a slow and difficult healing process, but it is taking place.”On government prospects for cutting the budget deficit, Mr Cameron said the government was "on the right track”."People are very understanding of the difficult inheritance we had - a record budget deficit, the biggest of anywhere in the developed world,” he said.