The Department for Work and Pensions has been criticised for advertising nearly 3,000 jobs on short-term contracts less than two months after shedding thousands of permanent staff.

A total of 3,824 permanent staff members across England, Scotland and Wales left under a voluntary exit scheme in late June. On Thursday, the DWP said it was looking to recruit 2,800 people to work on its “reform programmes”.

Mark Serwotka, the general secretary of the Public and Commercial Services union, which represents public sector workers, said: “It is incredible that less than two months after cutting thousands of low-paid jobs, the DWP is advertising for close to the same amount.

“Instead of constantly trying to trip up claimants, the DWP should ensure the proper resources are in place to return the department to one where sick, disabled and unemployed people are given the support they need and deserve.”

A PCS spokesman told the Guardian: “We see this as further casualisation of the workforce, which we are obviously opposed to. We want to see people employed on permanent contracts.”

According to the union, many of the staff who left in June worked in areas similar to those in which the department is now seeking to hire. It said the work could have been done by the existing staff, “with minimal retraining and setup costs”.

Its analysis suggested that the first wave of hires would mean a shift in the department’s geographic focus.

London and central England in particular are recruiting significantly fewer than they lost in June, while many more will be hired in north-west England and in Wales than those who left in those areas.

A DWP spokesman said: “We are undertaking some big welfare reforms and we’re recruiting fixed term 18-month appointments to cover this period. There have only been a handful of compulsory redundancies over the last four years – with the vast majority of people leaving voluntarily.”

The news comes as the DWP deals with a row over its use of fake benefits claimants to send out a positive message about its reformed benefits system.

It used stock images alongside what it admitted in a response to a freedom of information request was invented testimony. The department said they were representative of conversations its staff had had with real people.