The number of young people signing on in some parts of Scotland has doubled and in one area trebled in little more than a year, new figures show.

Statistics also revealed that 10,000 jobs have been lost in the Scottish construction sector in the three months to June.

Labour said the figures showed the Coalition Government’s economic plans were not working and ramped up calls for a so-called Plan B.

But Tory and LibDem ministers insisted they were sticking to their policies and the most important priority was reducing the budget deficit.

It came as a union accused UK ministers of attempting to exploit the unemployed over plans to make those on the dole for more than two years carry out community service.

The figures for youth unemployment will be seen as particularly worrying. The number of young people unemployed is now touching almost a million across the UK.

The statistics, which break down areas by Westminster constituency, show the UK’s worst affected area is Stirling, where the number of 18-to 24-year-olds claiming jobseekers allowance has more than trebled – from 55 when the Tory-Lib Dem Coalition came to power in May 2010 – to 175 in September.

Youth unemployment almost trebled in Dundee West as well, from 120 to 295. It more than doubled in Falkirk and Aberdeen South, rising from 135 to 310 and 35 to 75 respectively.

Across the UK as a whole the figures jumped 7.9% over the same time period. In more than 30 parliamentary constituencies the figures have more than doubled, but it was only in Stirling where numbers trebled.

Anne McGuire, Labour MP for Stirling, raised the issue at Scottish Questions in the House of Commons yesterday. But Scottish Secretary Michael Moore, said youth unemployment had increased under the last Labour government as well.

The research looked at the number of 18 to 24-year-olds on jobseeker’s allowance for more than six months. Similar figures released earlier this week showed the number of young people out of work has doubled in half of Scottish local council areas since 2007.

Labour’s Shadow Scottish Secretary Margaret Curran said: “Scots are facing a double whammy from the Tories cutting too far, too fast and an SNP Government presiding over stagnant growth and risky cuts in capital spending. Scotland has a jobs crisis and a growth crisis.

“If the two governments won’t follow Labour’s five-point plan to boost jobs and growth in Scotland, we need to hear specific new action to bring jobs and growth back to the Scottish economy.”

The row came as Work and Pensions Secretary Iain Duncan Smith refused to quash reports he threatened to resign over possible changes to benefit rises. The former Tory leader sidestepped questions, suggesting he was at loggerheads with the Treasury over claims it was examining ways to halt a big rise in payments next April.

Mr Duncan Smith told the Commons Work and Pensions Committee: “I try not to threaten anything really. I try to do things rather than threaten.”

The claims follow speculation the Treasury is preparing to change how it increases benefits in line with inflation, to save up to £1.8 billion.