The flagship national scheme to tackle youth unemployment has paid out for less than 4,700 placements for its target group of 18- to 24-year-olds who have been out of work for more than six months.

The figures, released by the Department for Work and Pensions (DWP) on Monday, are the first official statistics on take-up of the youth contract, which was announced with some fanfare by Nick Clegg 18 months ago.

The deputy prime minister last week appeared to presage the disappointing numbers by announcing a cross-government review of measures to tackle youth unemployment, an implicit admission that the youth contract has not worked.

The scheme offers businesses a subsidy of up to £2,275 for taking on a young person who has been out of work for at least six months.

The DWP said wage incentives had been handed out to employers for more than 4,690 recruits between June 2012 and May 2013.

The youth contract was designed to help 160,000 young unemployed find work over three years – about 53,000 a year.

The DWP said the scheme "has encouraged UK businesses to offer over 21,000 jobs to young people at risk of long-term unemployment". The bulk of wage incentive payments can usually only be claimed after someone has been in work for six months.

Since the scheme's launch in April 2012, youth unemployment has fallen by 59,000 and the number of young people claiming jobseeker's allowance is down by over 67,000. However, the low take-up means the fall in youth unemployment cannot be attributed to the wage subsidy.

One source in the Conservative wing of the DWP said: "It is no secret that this is something Nick Clegg was very keen on. For one reason or another, there has been very little take-up. It may be small employers are saying that they have no need to take on someone who has been unemployed for more than six months.

"We have done everything possible to reduce the bureaucracy involved with the scheme and to publicise it, but these figures are disappointing."

The source said other DWP efforts to deal with youth unemployment, such as work experience schemes, were effective.

Mark Hoban, the employment minister, said: "Although take-up of the incentive got off to a slow start, it is now on a clear upwards trajectory – and of those employers who have already made use of the scheme, 86% said they would be likely to take someone else who is eligible for the scheme on in the future."

Mike Cherry, national policy chairman for the Federation of Small Businesses, said: "[Our] research found that a wage subsidy is the single most important thing the government can do get small firms to take on more employees.

"Small businesses are committed to employing young people where possible and wage incentives can make a difference. More can always be done to make small businesses aware of the support that is available to them, and the FSB will play its part in doing so."

When it launched the youth contract, the government committed to review the progress of the measures on an ongoing basis. Ministers will shortly announce how any money not claimed by businesses in wage incentives is to be reinvested in other programmes to help young people into work.

Hoban said: "We have vigorously promoted the wage incentive to employers, and the response has been increasingly positive.

"But we've always been clear that we'd listen to employers and see how the policy is working. Any money which is not claimed in wage incentives will be reinvested in other programmes to help young people into work."

The shadow work and pensions secretary, Liam Byrne, said: "The youth contract has utterly failed to get our young people back to work. This flagship scheme is on course to miss its target by more than 92% – no wonder there are still almost a million young people out of work.

"The welfare revolution we were promised has fallen apart. The work programme doesn't work, universal credit is disappearing into the sunset, and now we know that the youth contract has been a disaster."