Prime minister had praised ill-fated Advantage WM and other Midlands award winners as examples of 'big society' in action

A quango that David Cameron praised as one of the organisations that will "bring the wealth, the jobs and the opportunity our country needs so badly" is being scrapped with the loss of more than 300 jobs.

The prime minister sent a video message praising Advantage WM after it won a top prize at the Midlands Excellence awards earlier this month.

"These awards celebrate precisely the kinds of things that will get our economy back on its feet," Cameron told the audience on a video link. "You are the doers and the grafters who are going to bring the wealth, the jobs and opportunity our country needs so badly."

However, most of the 340 staff who worked for Advantage WM expect to be made redundant in September and the organisation, which has an annual investment budget of £300m, will be wound up in March next year.

"For once, I agree with the prime minister, or rather, he agrees with us," said Mark Serwotka, general secretary of the PCS union. "Like the other RDAs [regional development agencies], Advantage WM plays a vital role in the economy and this is exactly the sort of alternative to spending cuts that we've been talking about. Instead of arrogantly swinging the ideological axe, the government should be investing in the public sector to help our economy to grow."

Cameron was forced to relaunch his "big society" project this week after allegations the government's cuts were hitting public sector and voluntary groups that deliver local services.

During his address to the awards ceremony he appeared to acknowledge that organisations such as Advantage WM had a role to play in the "big society".

"Everyone in your room tonight has a huge impact on our society and our culture and it is great that those who take their responsibility seriously are really being recognised. That is one of the things the big society should be all about."

Advantage WM won the main public sector award at the Midlands Excellence ceremony at Birmingham ICC on 3 February.

Mick Laverty, chief executive of Advantage WM, said the award was testament to the professionalism and commitment of the agency's staff. "We have made a difference. Independent evaluation has shown that every £1 invested by the agency generates an average £8.14 return back into the region's economy - as public sector activity goes that's an outstanding return."

The government is scrapping RDAs and replacing them with local economic partnerships. In November Vince Cable, the business secretary, described the abolition of RDAs as "a little Maoist and chaotic".