The jobless total jumped by 7,000 to 2.52 million, ending a run of reductions, with all the increase caused by more 18 to 24-year-olds becoming unemployed.
Unemployment has increased for the first time in a year, delivering a pre-Budget blow to the Government.
The total is still 152,000 lower than a year ago, while the number of people claiming jobseeker's allowance fell in February by 1,500 to 1.54 million, the fourth consecutive monthly reduction. There were 993,000 jobless 16 to 24-year-olds in the latest quarter to January, up by 48,000 from the three months to October, but the rise among 18 to 24-year-olds was 53,000.
The number of unemployed women increased by 5,000, the latest data from the Office for National Statistics showed. Other figures revealed that public sector employment fell for the 13th consecutive quarter, by 20,000 to 5.7 million, the lowest for over a decade.
Employment Minister Mark Hoban said: "It's a credit to businesses that the private sector is employing one and a quarter million more people than when this Government took office, helping us compete in the global race. Today's figures show that, against a difficult economic backdrop, we're helping people to move off benefits and into work."
But Dave Prentis, general secretary of the Unison union, said: "This time five years ago there were one million fewer unemployed people in the UK. The Government has failed every single one of these people - and it has failed our country."
Meanwhile, the Chancellor has announced an Employment Allowance of £2,000 a year towards employer National Insurance contributions under moves to boost jobs.
George Osborne told MPs that the Government was taking tax off jobs, which would particularly help small businesses who wanted to hire their first employee or expand their workforce.
From April 2014, all businesses and charities will be eligible for the new allowance, which will reduce their National Insurance contributions (NICs) bill. Up to 2.5 million employers will benefit, while 450,000 of the country's smallest businesses will no longer pay any employer NICs.
Employers with fewer than 10 members of staff will see their employer NICs bill cut by £805, said the Treasury. Under the announcement, every business will be able to employ one worker on a salary of £22,400, or four employees on the minimum wage, without paying any employer NICs.