The number of unemployed rose by 60,000 in the three months to June
The number of people out of work for a year or more could almost double by the end of 2009, the TUC has warned.
The trade union organisation predicted a sharp rise in the number of long-term unemployed to 700,000, and that the jobless total would pass two million.
It was up to unions, employers and the government to halt and reverse the upward trend of recent months, it said.
The warning comes as latest figures are expected to show a further increase in the number of unemployed.
But Employment Minister Stephen Timms said the foundations of the UK's labour market "remain strong".
The TUC said the government's welfare reforms to toughen the benefits regime for lone parents and disabled workers would lead to more people sliding further into poverty.
TUC general secretary Brendan Barber said: "Employment levels have remained high despite the recent economic turbulence and are nowhere near the dark days of 1992, when nearly three million people were unemployed.
"However, the TUC is concerned that unemployment has been sneaking up in the last few months and it's up to unions, employers and the government to halt and reverse this trend as soon as possible.
"With unemployment rising, people are looking to the government for a response, and economic measures will be far more welcome than yet another round of welfare reforms."
Last month official figures showed the number of people out of work rose by 60,000 to 1.67 million in the three months to June, taking the unemployment rate to 5.4%.
Mr Timms said: "The UK is facing up to global economic challenges as are many other countries.
"However, the foundations of the UK labour market remain strong, there are still jobs for people and significant support through Jobcentre Plus to help people get back to work quickly."
He added: "Our welfare reforms are about making sure that no one on benefits is written off. They are radical, long-term plans to help reach our goal of getting a million people off incapacity benefits by 2015.
"While we accept these are difficult economic times, it would be wrong to suggest that disabled people, lone parents and other long-term benefit claimants should simply be put on the scrapheap."