Almost a million people will have been out of work for more than a year by the end of 2012, according to new research.
The Institute for Public Policy Research (IPPR) said another 107,000 people will join the ranks of the long-term unemployed in the coming months, taking the total to its highest level since 1995.
The report, published ahead of new unemployment figures, said long-term unemployment was the "hidden crisis" facing the UK economy.
Tony Dolphin, the IPPR's chief economist, said: "On current progress, two-thirds of people out of work for a year will not get work in the following two years. Government policy is not keeping pace with joblessness.
"Unemployment is not going to fall until the middle of 2013 and the number of people out of work for over a year will grow to almost a million by the end of this year."