BUDGET COVERAGE Live video and text coverage of the Budget - with full analysis and reaction as it happens - begins on the BBC News website at 1130, with Mr Darling due to begin his speech in the Commons at 1230. BBC2's coverage is from 1130 to 1445 and there are Budget specials from mid-day on BBC Radio 4 and 5 Live
And he is likely to point to an IMF report which will suggest Britain's recession this year will be less deep than some other major industrial nations.
"The Budget will make a prudent provision for potential losses from banking interventions in line with our cautious approach to forecasting the public finances," the spokesman said.
Before departing for the Commons, Mr Darling briefed cabinet colleagues on the contents of his second Budget as chancellor.
Mr Darling will reveal his own estimate of the bail-out cost - reported to be more like £60bn - when he delivers the Budget.
The prime minister's official spokesman said the cabinet was in a "realistic and determined" mood after being briefed by Mr Darling.
Borrowing forecasts
The top Budget priorities were growth, jobs and "investment in the economy of the future", he added.
Weeks ahead of his second Budget as chancellor, Mr Darling had already acknowledged that the recession would be worse than he had predicted.
'Too weak'
In his new economic forecast on Wednesday he is expected to revise his predictions of last November that the economy will contract by between 0.75% and 1.25% of Gross Domestic Product in 2009.
He stressed the government must intervene to stop people losing their jobs becoming long-term unemployed.
If, as expected, he now predicts a slowdown of as much as 3.5% of GDP - it would make this the worst recession since 1945.
Conservative leader David Cameron said the Budget represented a "day of reckoning" for the government, proving that its economic policies had not worked.
He is also expected to revise his public sector borrowing forecasts, as tax revenues fall.
He told BBC News: "We've got to get debt under control, we've got to start to close that deficit, and... I think this government is just too weak to do the job."
Experts believe his £118bn prediction for borrowing for 2009-10 could be increased to as much as £160bn.
Mr Darling is expected to explain how he intends to get the public finances back on track - possibly with future tax increases and spending cuts that would come in after the next general election.
BBC Political Editor Nick Robinson said: "Today he has to say a little bit about a future squeeze on spending and future tax rises.
"But...he will be very political. He is a Labour chancellor and what he will say is he wants the wealthy to take the burden."
Mr Darling has already announced a new 45% top rate of income tax from April 2011 on earnings over £150,000 - which he hopes will raise £1.6bn a year, although the Institute for Fiscal Studies has predicted it will only raise about £550m.
'Few easy wins'
The VAT rate, temporarily lowered to 15% last December, is due to go back up to 17.5% at the end of the year and there has been speculation that it may go up further, to 18.5%.
The Treasury also says it could make £15bn spending cuts through "efficiency savings" from 2010 - although a report from a panel of independent advisers to the Treasury warned the government there would be "few easy wins" and the projected savings were not certain.
The full benefits of "sustained action" would not be seen until 2013-14, they said.
The proposal has annoyed the Public and Commercial Services Union, whose general secretary Mark Serwotka said the government should concentrate on getting tax from the "super rich" and big corporations.
"The government calls these efficiency savings but let's be clear, they are real cuts that will affect public services, people's jobs, livelihoods and pensions," he said.
Mr Darling has already indicated there will be help for employers to save jobs and there have been suggestions there will be a car scrapping scheme, which could see people get £2,000 to trade in their old cars for new.
He could also claw back tax relief on the pensions of top earners, although this is only likely to affect those on £100,000 a year or more.
Housing package
Gordon Brown has said the Budget will plot a "green" route to economic recovery. Mr Darling is expected to announce the world's first legally-binding budgets for greenhouse gases in an effort to get the UK to cut emissions by between 34% and 42% by 2022.
A £1bn package aimed at boosting house sales and house building is expected to include a three-month extension on the stamp duty "holiday" on homes costing below £175,000, which will remain in place until the end of the year.
Liberal Democrat Treasury spokesman Vince Cable said people needed "a very clear statement - without spin - about exactly what the situation is in the economy".
Liberal Democrat Treasury spokesman Vince Cable said people needed "a very clear statement - without spin - about exactly what the situation is in the economy".
He told BBC Radio 4's Today programme he was concerned about when the economy would get back into balance, in light of falling tax revenues from the financial and housing sectors.
There was grim news on the jobs front ahead of the Budget, with unemployment figures showing the number of people looking for work has reached 2.1 million - its highest level since Labour came to power in 1997.
The challenge to politicians of all parties was to show "how public expenditure is going to be tightly disciplined over the next Parliament and beyond", he added.
Car scrapping
Shadow chancellor George Osborne said the estimates of the cost of the bank bail-outs showed the "potentially massive cost of Gordon Brown's utter failure to regulate the banking system".
Meanwhile, official figures showed that public borrowing soared to a record £90bn in the last financial year - almost 6.2% of national income and far higher than the £78bn prediction made by Mr Darling in his pre-Budget report last November.
The Tories say the Budget will be a "day of reckoning" which will "lay bare" Labour's economic failings.
Mr Darling is expected to plug part of the gap in the public finances with £15bn of "efficiency" cuts from 2010 - after the next election - provoking anger from public service unions.
Mr Osborne has urged the chancellor to focus on how to reduce government debt rather than "short-term political pressures" ahead of a likely election in 2010.
He could also claw back tax relief on the pensions of top earners, although this is only likely to affect those on £100,000 a year or more.
There is also likely to be a car scrapping scheme, which could see people get £2,000 to trade in their old cars for new, in an effort to boost the floundering motor industry.
A £1bn package aimed at boosting house sales and house building is expected to include a four-month extension on the stamp duty "holiday" on homes costing below £175,000.
From 1pm we will have tax, pension and personal finance experts available to answer your questions about the Budget and how it affects you. If you have a question you can send it to us using the form below:
From 1pm we will have tax, pension and personal finance experts available to answer your questions about the Budget and how it affects you. If you have a question you can send it to us using the form below:
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