Unemployment could be as high as 6.3m in the UK if a different counting measure was used, highlighting the true scale of joblessness, according to a report.
The TUC said the higher figure - more than twice the official total - was revealed using an American measure, which includes people in part-time jobs because they cannot find full-time work and recent redundancies.
The jobless total increased to 2.68m last month and is expected to rise again when new figures are published by the Office for National Statistics on Wednesday.
But the TUC study suggested the actual number of unemployed people in the UK could be 6.3m, which would be higher than any point since the early 1990s.
Under-employment, which counts those doing temporary or part-time jobs, has risen to a record 1.9m, according to the research.
The TUC said temporary jobs were better than unemployment, but added that they tended to be low paid, insecure and offered little or no career prospects.
Officials called on the Government to acknowledge the scale of the jobs "crisis" rather than repeat the "ill-informed" claim that there were plenty of jobs available.