Around 140,000 local authority jobs are expected to be axed in the next year because of spending cuts, council leaders warned today.
The Local Government Association had predicted that 100,000 posts would go across England and Wales after Chancellor George Osborne set out the broad framework for public spending in the June budget.
But the association said today that the Government's decision to front load a large proportion of the cuts into the first year, rather than allow councils to spread them evenly over the four years of the spending review, was likely to lead to more jobs being lost.
The "unexpected severity" of the first-year cuts means councils will have to trim their budgets by an average of 11% in 2011/12, said the LGA.
Some authorities will also have to deal with the "difficult impact" of the loss of the Working Neighbourhoods Fund, which channelled £450 million to different parts of the country.
The LGA called on the Government to ease the effect of reductions in next month's local government finance settlement so that councils could spread the cuts more evenly over the next four years.
Baroness Eaton, chairman of the LGA, said: "Local councils knew the cuts were coming and had planned prudently to reduce spending over the coming years.
"We cut more than £1 billion from our budgets in the middle of this year, rolled up our sleeves and got on with the job. But the unexpected severity of the cuts that will have to be made next year will put many councils in an unprecedented and difficult position.
"No council cuts jobs lightly, but many are being left with no choice. Some jobs will go in natural wastage, not filling vacancies and voluntary redundancy. However, we cannot escape the fact that some losses will be dedicated professional posts that, given a choice, councils would not want to see go. These are the tough choices we are going to have to make.
"Local government will have to make cuts next year of around £2 billion more than we anticipated just a month ago. This stifles the opportunities for innovation and means town halls will be forced to cut further and deeper next year than they first thought.
"In order to protect frontline services, the Government must ensure that councils have the flexibility needed to manage changes to grant funding that are heavily loaded at the beginning of the four-year settlement period. Grants that have yet to be finalised must be set at levels that help councils, rather than making a difficult situation even worse."
Unions have attacked the scale of job losses announced already in scores of councils, saying the figure had already passed the 50,000 mark.
The GMB said 50,665 job losses or threats of redundancy had been made by 45 councils in England in recent weeks.
National officer Brian Strutton said: "Local government frontline services will be badly damaged by 140,000 job losses predicted by LGA for next year.
"The Tory/Liberal Government has taken an almighty gamble with people's livelihoods by cutting public spending instead of putting the priority on growth and getting the unemployed back to work. It is not possible to deflate the economy back to growth and a balanced budget."
A spokesman for the Communities and Local Government Department said: "The local government finance settlement is due shortly and will be announced in a statement to Parliament. We are not going to pre-empt that statement and any commentary ahead of formal publication is pure speculation and in this case scaremongering.
"We are working towards delivering a settlement that will help to protect frontline services and the LGA would be well placed to focus their efforts on working with councils to do the same."
A Whitehall source said the Government believed councils could protect frontline services, especially if they cut "non jobs" and tackled high salaries among senior officers.
Dave Prentis, general secretary of Unison, said: "These cuts are front-loaded, so that hundreds of thousands of council jobs are being axed, devastating services and deflating the economy.
"Hard-hit local communities struggling to ride out of the recession are being dealt another blow by the Government.
"It is shocking how savage and unnecessary these cuts are, when we know that there is an alternative. The Government should be protecting frontline services, not wielding the axe over jobs and the future of the most vulnerable in society."