The number of Scots without a job has fallen again and the number in work has continued to rise, but there are growing concerns over how long the figures can remain positive in the recession.

According to official data, the number of people who are out of work and receiving Jobseeker's Allowance fell to 142,600 in July – a drop of 800 from the previous month.

When measured by people out of work but not eligible for benefits, the figures show 214,000 Scots are jobless, a drop of 5000 over the period from April to June.

The Scottish unemployment rate now stands at 7.9%, compared with 8% for the UK as a whole.

But unemployment north of the Border is still 3000 higher than the same quarter last year.

Last night, leading economists said they were baffled at the way employment statistics continued to buck other trends, although they suspect growing numbers are in part-time work or working fewer hours than they would wish.

Unison also suggested there was a rise in controversial "zero-hours contracts" where people are on call with no guarantee of weekly hours.

Professor Brian Ashcroft, economic editor of the Fraser of Allander commentary – who has blogged at his scottisheconomicwatch site about the puzzling contradictions between the economic indicators and employment figures – said part of the reason for employment holding up might be that productivity could actually be falling due to strains in the system.

"That would mean that more jobs are required to maintain output, and that would be very worrying and would mean we have less spare capacity than we thought in the event of recovery," he said.

Meanwhile, the Scottish TUC pointed to figures showing there are 240,000 Scots now underemployed.

"These are people who either want more hours in their current job, or want an additional job, or a new job giving them more hours," said STUC assistant secretary Stephen Boyd.

General secretary, Grahame Smith, said there was little cause for celebration in the figures. "Youth unemployment continues to rise, underemployment is at historically high levels, real wages continue to decline and unemployment remains double pre-recession levels," he said.

"Despite the recent improvement, employment remains significantly below pre-recession levels and too many new jobs being created are part-time, low-wage and insecure."

He added: "There is little prospect of a genuine and sustainable improvement in the Scottish labour market without a wholesale revisiting of the UK Government's economic strategy."

CBI Scotland policy executive Lauren Paterson said: "Despite the challenging economic times, the Scottish labour market is showing resilience, with jobs being created and fewer people unemployed."

She said the figures indicated that the private sector was gradually regaining the confidence to hire and called on the Scottish Government to ensure this trend continued.

Liz Cameron, chief executive of the Scottish Chambers of Commerce, said it was "undoubtedly good news" that unemployment had fallen for the fifth month and the number of people in work had risen again.

She said this reflected the "resilience of the Scottish economy and the key role the private sector is playing in ensuring Scotland retains as many skills as possible in our workforce".

However, there was a more sceptical take among opposition politicians. Cathy Jamieson, Shadow Economic Secretary to the Treasury, said: "While the slight fall in unemployment over the last quarter is welcome, there are still too many people under-employed or out of work.

"The fact there are 3000 more unemployed people than this time last year highlights that the Scottish economy is still in bad shape."

Ms Jamieson added: "In particular, the sudden rise in male unemployment is of concern and we must ensure that any strategy to tackle unemployment does not overlook anyone who is out of a job and wants to work."

Willie Rennie, leader of the Scottish Liberal Democrats, urged the Scottish Government to do more to promote a Westminster scheme that aims to help young unemployed.

Mr Rennie said: "It is good to see both Scotland and UK unemployment numbers decreasing at the same rate but thousands still remain out of work.

"This makes it all the more necessary that both of Scotland's governments work hand-in-hand to promote jobs at every opportunity.

"They should especially promote projects like the £1 billion UK Youth Contract that helps young people find work and training opportunities."