Merseyside would be the hardest region hit, as it has the highest proportion of public sector jobs in the UK.

Mr Barber said: “Spending cuts will hit both public and private sectors.

“Areas such as Merseyside, in particular Liverpool, which have a high proportion of public sector jobs, would be right in the unemployment firing line.

“Prolonged mass unemployment would not just do economic damage, but would have terrible social effects.

“I don’t think that Britain is broken, but this would be one way to break it.

“Last time we suffered slash and burn economics, we had riots in the streets here in Liverpool.

“I make no prediction that this would happen again, but it would take us back to the days of a deep North–South divide and once again hollow out whole areas of the economy.”

Mr Barber said spending cuts would lead to a "double quick, double dip" recession. The TUC Congress, which starts today, will be the last one before the next general election.

It was last held in Liverpool at St George’s Hall, in 1906.

Prime Minister Gordon Brown will speak to delegates on Tuesday and is expected to deliver an upbeat message, declaring the country is “on the road to recovery”.