The Government has refused requests to reveal which companies are involved in delivering controversial "workfare" policies in Scotland – despite having already published similar information in England.

The Department for Work and Pensions (DWP) has faced criticism for increasing use of Mandatory Work Activity (MWA) placements for job seekers, requiring those on benefits to take up voluntary work, unpaid work placements or lose their support.

The scheme sees job seekers referred on to intermediary companies who offer them the chance to work unpaid for up to eight weeks. Providers of the work placements have included major multinationals and large retail chains, but some firms have faced criticism for taking advantage of the programme.

Critics warned it could even depress the creation of "real" jobs. Tesco blamed an error last week for an advertisement for night shift work that listed pay as JSA [Jobseeker's Allowance] + expenses.

Meanwhile, firms such as TK Maxx, Sainsbury's and Waterstones, which have taken part, have pulled out. Matalan suspended its involvement on Saturday and Poundland, which faces a court case over the issue, is said to be reviewing its policy.

Housing charity Shelter Scotland said it had backed away from the programme last year.

The Herald has been requesting, through Freedom of Information, the names of companies involved in the provision of unpaid placements for job seekers since early last month.

The request was turned down last week by the DWP, which said providing it would compromise the "commercial interests of both the department and those delivering services".

The refusal said the DWP considered there was no public interest argument for releasing the information requested for what is known as the Scotland Contract Package Area (CPA). But these concerns only appear to apply in Scotland. The DWP has published the names of the companies which provide mandatory work placements in south-east England and north- west England CPAs.

In December, the DWP revealed that in areas of south-east England such as Kent, providers of unpaid work placements include Asda, Oxfam and Pizza Hut.

Tom Greatrex, Labour MP for Rutherglen and Hamilton, will today lodge questions in the House of Commons asking why similar information is being withheld in Scotland.

He will call again on the DWP to reveal which firms it is working with to deliver the Work Programme. Mr Greatrex said: "It is astounding that the DWP are refusing to release this information in relation to contracts in Scotland when the same information is available for England.

"As these are contracts funded through public money, people have a right to know which companies are involved."

A spokeswoman for the DWP denied the decision was inconsistent, adding: "Scotland is not being treated as a separate case. In line with the Freedom of Information process, we have been asked to review this decision and that is what we are currently doing."