Jeremy Corbyn has called on ministers to halt the closure of job centres and social security offices as he continued a five-day tour of key constituencies in Scotland.

The Labour leader addressed a rally in Coatbridge, North Lanarkshire, where the Department of Work and Pensions is closing an administration office and relocating 250 jobs as part of a UK-wide cost-cutting and restructuring programme.

Speaking to about 250 union activists and supporters outside the Quadrant shopping centre, where a large proportion of stores are shuttered and vacant, Corbyn said the DWP closure would damage the small town’s economy.

“I’m saying to the government: halt this closure programme, halt the closure of this centre here, don’t destroy the 600 jobs that are available here that are important as an economic contributor to this town,” Corbyn said. “Instead think again. Think about the role of government in supporting people. Think again about the punitive way in which you operate your regimes.”

He repeated Labour’s pledge to lift the cash freeze imposed on most benefits, which normally rise each year in line with inflation – though party sources stressed they would not be able to meet the full cost of cancelling it immediately. Labour believes part of the cost could eventually come from the increased tax contributions by workers paid the party’s proposed £10 an hour minimum wage.

The Conservatives hit back by issuing a statement accusing Corbyn of making promises he could not afford to deliver. “Labour spent their whole election campaign promising the country things they simply couldn’t afford and they’re doing the same thing again,” it said. “Ending this freeze would cost a massive £12.9bn and leave ordinary, hardworking people footing the bill.”

The rally was organised by the PCS, the public sector union that is not affiliated with Labour but supports Corbyn’s leadership.

Gillian Jones, the PCS branch secretary, said its survey of the DWP staff being relocated had found they spent thousands of pounds each week in local shops. “The loss to this community of these jobs is going to have a huge impact,” she said. “We work here, we shop here, we socialise here. We’re very much part of this community and that’s very much the way we want to keep it.”

Corbyn is visiting 18 Scottish constituencies on a five-day tour that Labour hopes will bolster the party’s unexpected victories in seven Scottish constituencies in June’s snap election in case a second election is called.

Labour gained ground after 10 years of decline that culminated in the humiliating loss of 40 of its 41 Westminster seats to the Scottish National party at the 2015 election. Corbyn’s advisers say they underestimated the scale of his appeal in Scotland and the SNP’s vulnerability.

Members of the public gather to listen to the Labour leader Corbyn in Coatbridge. Photograph: Jeff J Mitchell/Getty Images

On Wednesday, Corbyn travelled to the Western Isles, which Labour believes it could regain from the SNP. He visited seats in Glasgow on Thursday, taking in a rally with younger supporters at a brewery, followed by a filled-to-capacity speech at Glasgow central mosque.

Corbyn told activists in Glasgow “a Labour government would not be afraid to pick up the phone to President Donald Trump and say quite simply ‘you are wrong on the Paris climate change agreement. And we would also be quite open in saying ‘When the Ku Klux Klan and the fascists arrive in Charlottesville, the whole world should condemn them’.” His tour ends in Edinburgh on Sunday, with an event at the fringe festival.

The seat of Coatbridge, Chryston and Bellshill was won back by Labour in June after it was seized by the SNP in 2015. Its new MP, Hugh Gaffney, a trade union activist and former postman, wore his old ParcelForce shirt in his maiden speech at Westminster where he called for the Royal Mail to be renationalised.

Corbyn said the UK government needed to abandon its “often punitive sanctions regime” against those claiming benefits and should overhaul the universal credit system.

“Invest in the future of all us. Invest in better transport systems; invest in sustainable jobs in new industries; invest in communities; invest in decent housing. You then create the virtuous circle of increasing employment in all those industries and providing a common good for all,” he said.

“You don’t cut your way to prosperity: you improve people’s lives by investing in the future. If money was found to bail out the banks then surely the money should be available to support and invest in communities all across the country.

“[If] you cut and destroy public services, they are not there for anybody later on in life. Even the very richest get heart attacks; even the very richest may get cancer; even the very richest homes might catch fire. At that point they need an ambulance service. At that point they need a hospital. At that point they need a fire service. I simply say to the Tory party, think again about the direction you’re taking the country in.”