More than 30 per cent of people who start apprenticeships in Britain fail to complete them, and the numbers have worsened every year for the past three years.

The data on “success rates”, which the Financial Times has drawn from official spreadsheets, raise questions about the government’s flagship policy to boost the number of apprenticeships to improve the skills of Britain’s workforce.

The government has highlighted the fact that it created more than 2m apprenticeships in the previous parliament and has promised to create another 3m by 2020. However, its figures refer to the number who start apprenticeships, not the number who successfully complete them.

The success rate for all apprenticeships was 68.9 per cent in 2013/14, the latest year for which data are available. It has declined steadily since 2010/11 when it was 76.4 per cent.

If the success rate stays as it is over this parliament, the 3m target will equate to less than 2.1m successfully completed apprenticeships.

Neil Carberry, the director for employment and skills at the CBI business lobby group, said the statistics were “a timely reminder that while the government targets 3m starts, it’s completions that matter to companies and participants”. He said businesses wanted to see more “high quality” apprenticeships that were routes to good careers.

Peter Kyle, a Labour MP and a member of the Business, Innovation and Skills select committee, last year asked the government if it would set a target for apprenticeship achievements. Nick Boles, the skills minister, replied: “We are establishing a new Institute for Apprenticeships to safeguard quality but do not intend to set a target for achievements.”

However, one official, who spoke on condition of anonymity, said the quality of the apprenticeship system should be judged as much by the numbers who complete apprenticeships as the numbers who start them — “in fact, more so”.

The person said success rates were important because they helped to indicate whether the initial careers and recruitment advice was working, whether the training was “up to scratch” and whether apprentices “genuinely view their apprenticeship as a stepping stone to a rewarding career”.

Last year Ofsted published a damning assessment of the system, saying too many employers and providers had been using taxpayer-funded apprenticeships to accredit existing employees for skills such as making coffee and cleaning floors.

The sharpest fall in success rates was among apprentices aged 19 and over, which fell 4.4 percentage points in the latest year alone to 68.2 per cent. The success rate for under-19s fell 0.4 points to 71.1 per cent.

Mr Kyle said the fall in success rates was “alarming”. “The government needs to address this to ensure that investment in apprenticeships contributes to a much-needed improvement in our economic productivity.”

The Department for Business Innovation and Skills said the government had not published any research into why the success rates were deteriorating.

However, it suggested it could be linked to the government’s attempt to drive up standards. In August 2012 it changed the rules so that apprenticeships had to last at least 12 months and involve some off-the-job training.

“Our reforms mean apprenticeships are now more rigorously tested, last longer and are more responsive to the skills needs of industry,” the DBIS said.

The government plans to pass the costs of its apprenticeship programme to employers, much to their annoyance. From April 2017 every employer with a pay bill of £3m or more will have to pay an “apprenticeship levy” — a 0.5 per cent tax on their payroll. Employers will be able to reclaim vouchers from the government that they can spend on apprenticeships.

The government says the levy will encourage more companies to hire apprentices and drive up quality by putting employers in charge of the training they buy. Employers will also run the Institute for Apprenticeships, charged with approving standards and assessment.

Many companies fear the government is more focused on quantity than quality because it wants to meet its 3m target.

Mr Carberry of the CBI said: “Ensuring the new Institute for Apprenticeships focuses on increasing the numbers of completions of high quality schemes will be essential.”

Some employers’ groups have warned that companies will simply rebadge their existing training as “apprenticeships”, which will boost the numbers without creating a real change in the workforce.