The Liberal Democrat party has admitted that it will not pay its interns a wage, more than a year after leader Nick Clegg promised that all party interns would be "properly remunerated" .

The admission from party staff comes after Lib Dem headquarters in Westminster advertised for a further slew of unpaid interns. Each position is expected to last three months at a time and slots have been advertised until May 2013.

A spokesperson for the party said that selection for places would be name and school blind but argued that they were "properly remunerated" as Clegg had promised, because expenses and lunch were being paid. Plans to provide bursaries for poorer candidates will not be available in 2012 due to lack of party funds.

Speaking to the BBC in April last year after the launch of new social mobility initiatives, Clegg said: "From now on, people who are advertising for internships in Liberal Democrat offices or Liberal Democrat MP will have to make sure that applications are name and school blind and there's proper remuneration so that we give new people opportunity to participate in that kind of political activity."

"The rules of the scheme do provide for proper remuneration in that they provide for lunch and travel expenses," a Lib Dem spokesperson said.

"Internships in business and politics have for a long time hindered social mobility, promoting the culture of contacts over ability and often only benefiting those people wealthy enough to live without a wage," they said.

They continued that although Lib Dem MPs would still be able to hire interns as they saw fit, a newly designed programme would be rolled out across the party.

"The internships are designed to be three months and to provide a number of different experiences of working for the party. The Liberal Democrat internship scheme is particularly aimed at recent graduates and all our internships are voluntary. There will be no contract to work set hours or undertake set tasks."

They said that they were "planning to bring forward proposals" which would look into paying interns, as soon as they could but could not give a date and did not have the money to currently do so.

"The Liberal Democrats are also committed to developing a bursary scheme to increase access opportunities, to support those from underrepresented backgrounds, but regret that no bursaries will be available for internships in 2012," they added.

The government's own legal advisors have warned that under minimum wage laws, many internships including those in MP's offices could be breaking the law because they remain unpaid and therefore exploitative under the law.

Labour MP Stella Creasy, who also pays her interns a living wage, warned that the Lib Dems could be breaking the law by not paying interns over such long periods of time. "The law is quite clear about what can be done by a volunteer and what should be paid work. And one would hope that the deputy prime minister and his team would understand those distinctions," she said.

Creasy said she was all for internships as long as they were structured properly. "I want internships because they are a great opportunity … What worries me about these kind of placements is that the length of time, the barrier that the cost of living is in London for people.

"Just because there are 50,000 out of work in London doesn't mean that they are still going to be able to do this. The fact that it then undermines the minimum wage... There are methods of doing this that uphold the national minimum wage and provide an opportunity," she said.

Tanya de Grunwald, author of How to get a graduate job in a recession said: "I don't know what the Lib Dems think they're playing at, continuing to use young people's labour without paying for it.

"Claiming they can't afford to pay their young staff is irrelevant and insulting – travel and lunch expenses are not a wage and nobody can live on that. The Lib Dems – and all the other parties – must find the money to pay the staff they need, end of story.

"In continuing to run unpaid internships, Nick Clegg and his party should know they are directly contributing to the graduate jobs crisis, in which hundreds of thousands of young people have already worked for nothing – and many more have been locked out of these 'opportunities' simply because they can't afford to work for free."