A new row over Iain Duncan Smith's remarks that the unemployed should "get on a bus" to find work flared up today, when a study found there were almost nine times more jobseekers than jobs in the city at the centre of the controversy.

The work and pensions secretary said last week that Merthyr Tydfil in south Wales was an example of a place where people had become "static" and did not know that if they got on the bus they would be in Cardiff an hour later, and could look for work there.

"We need to recognise the jobs often don't come to you. Sometimes you need to go to the jobs," said the former Tory leader, who was criticised by union leaders for "insulting" the unemployed.

Research by the Public and Commercial Services union showed there were 15,000 people in Cardiff chasing 1,700 jobs, while in Merthyr there were 1,670 unemployed people and 39 job vacancies, all temporary and part-time.

The number of people out of work in Merthyr and Blaenau Gwent combined was more than the total number of job vacancies for the whole of Wales, said the PCS. The vast majority of vacancies in Cardiff were temporary and part-time, mainly unskilled labouring, for just one or three weeks' duration, said the union.

The most popular vacancy on the day the union carried out its research last week was a Christmas job in a well-known store working four-hour shifts on Saturdays and Sundays for the national minimum wage.

Among the permanent jobs was work in a casino or bars. Neither offered help with journeys home afterwards and the last bus out of Cardiff leaves at 11.06pm, the union pointed out. "Workers from outside the city might be able to get the bus to work, but they would not be able to get home," said a spokesman.

"These figures prove it is not a question of people not being willing to work, there simply are not enough jobs for them to do – and there are unlikely to be any time soon because of the government's plans to cut public spending, including cutting 15,000 more jobs in the Department for Work and Pensions."

When people sign on, they have to agree to travel up to an hour by bus to find work, increasing to an hour and a half after six months, said the union. "Instead of vilifying the unemployed, the government should be creating jobs and opportunities to help people get back to work and to help our economy to grow. It should also put proper resources into jobcentres to help jobseekers find suitable employment," said the spokesman.

Duncan Smith said on Friday after the union criticism of his comments: "The unions are showing themselves to be totally out of touch with reality with these pathetic remarks. They seem to be suggesting that anyone who commutes to work is somehow doing the wrong thing.

"I would suggest they apologise and recognise that ordinary, decent people want to improve their lives and do the right thing for their families and so value work and get on the bus."

A DWP spokesman said: "We're making sure that people get the help they need to get back into work no matter where they live.

"Last month's employment figures showed employment increasing and over 400,000 job vacancies in the economy.

"Every day across the country, people are making decisions that balance the job they want and the distance they travel to get there.

"This flexibility is vital to the British labour market."