Hetal Mehta from the Ernst and Young Item Club predicts further economic decline.
The UK economy has "deteriorated dramatically" in the past three months, and is already in a recession, top forecasters have suggested.
The Ernst & Young Item Club says the economy will shrink by 1% next year, before growing by 1% in 2010.
The Item Club's chief economist, Peter Spencer, told the BBC: "Recession is already baked in the cake."
But one "bright spot" is that inflation is likely to fall, enabling the UK to cut interest rates further.
In other developments:
Mortgage lending in the UK fell to its lowest level for more than three and a half years during September, the Council of Mortgage Lenders said. A total of £17.7bn ($30.9bn) was advanced during the month, 10% less than during August and 42% below the level for September last year.
UK government borrowing soared to a record high in September, with net borrowing rising to £8.1bn - the highest for more than 60 years, according to the Office for National Statistics
Sweden became the latest European government to announce a bank rescue plan. Its $205bn package included credit guarantees and a bail-out fund
The chairman of French savings bank Caisse d'Epargne has quit over the loss of 600m euros (£466m) in a "trading incident"
Dutch banking and insurance company ING is to receive a 10bn euro ($13.4bn; £7.7bn) government cash injection
The head of the European Central Bank said the bank would do whatever was necessary to boost market confidence
South Korea revealed its own financial sector rescue package, worth $130bn
Figures showed China's economy has continued to slow. Growth fell for the third quarter in a row - down to 9% in the three months to September
In its forecast for the UK economy, Ernst & Young said that company profits had already been damaged by very high commodity prices.
While recent actions taken by the government to shore up the banking system were welcome, the credit crunch would hit the economy "very hard", it warned.
Mr Spencer said: "Even if equity markets stabilise and we begin to see capital flowing around the international financial system again, we are still looking at a domestic and global economy that will be in recession for the next 12 months."
However, Ernst & Young forecasts that with plunging interest rates, falling inflation, and a fundamentally strong economy, the recession will be "relatively short and shallow".
We desperately need a global solution given the heavy dependence of our banks and borrowers on cross-border banking flows
Peter Spencer, chief economist, Ernst & Young Item Club
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