Hundreds of thousands of people aged 25 or over are entering apprentice schemes – which can pay as little as £2.73 an hour – prompting fears the schemes have become a subsidised “numbers game”.

Apprenticeship programmes have become a policy for all three major political parties as a solution to youth unemployment. But figures from the Department for Business, Innovation and Skills (BIS) show that more than 350,000 of the UK’s 851,000 apprentices were over 25, with more than 50,000 aged over 50.

The statistics have stoked concerns that apprenticeships are losing their focus on young people entering the workforce, instead becoming a numbers game, and even a way for businesses to get government subsidies for work training which would already be undertaken.

The number of UK apprentices has risen from 491,300 in 2009 to 851,500 today – an increase of 73%.

However, the proportion of those over 25 has more than doubled – it was 19% of all apprentices in 2009/10, but now stands at 42%.

David Cameron has pledged to fund a further 3m apprenticeships through welfare cuts, having previously stressed the schemes needed to “focus particularly on young people”. Ed Miliband has also pledged Labour’s support for boosting apprentice numbers.

However, the Labour chair of the Commons BIS committee, Adrian Bailey, said that while apprenticeships for older workers were increasing, the same was not true for the young people the schemes were intended to target.

“[Apprenticeships for] under 25s has at best been stable, and for a while actually decreased,” he added. “These are the most hard to reach people. We have to pledge more money but I want to get away from the numbers game. Numbers of apprentices don’t mean we’re training people in the areas where there’s a shortage of skills.”

The Association of Colleges, which represents sixth-form and further education colleges, is concerned that Labour and the Tories have announced plans to further increase the number of apprentices.

Teresa Frith, senior skills policy manager for the association, said: “The fact there are 50,000 apprentices aged over 50 is not a bad thing in itself but the government needs to be sure that the training being provided is genuinely meeting the needs of the individual as well as their employer … Apprenticeships should be about providing worthwhile training, not hitting Whitehall targets.”

Tony Dolphin, of the left-leaning thinktank the Institute for Public Policy Research, said that successive governments have “got into a numbers game on apprenticeships”, adding: “By making more money available, they’ve raised the possibility that companies would use them for older people. It’s an indirect consequence of making more money available.

“Our worry is that these people aged 25 and over are not new to the job market and certainly aren’t completing their education. It’s just paying for on-the-job training for existing workers.”

Apprenticeship programmes can provide substantial subsidies to businesses for training, offering the full cost of training for 16- to 18-year-olds, and up to 50% of the cost for older workers.

Experts said that such subsidies risked wasting public money if they merely funded training that employees would be providing anyway, rather than establishing skills that would help workers through their careers.

Dr Susan James of Oxford University said many of the apprenticeships for over-50s were classed at the most basic level – confusingly known as “intermediate level” – a qualification roughly equivalent to five GCSE passes.

“The fact that they’re going in at intermediate level rather than advanced or higher does bring into question what skills they’re actually qualifying in the apprenticeship,” she said.

“They’ve been in the labour market for 20 years, but they’re entering at intermediate level.If they left school and didn’t get a qualification, and this is their first step to a more formal form of education, then great.

“[But] if it was training that the company was going to do anyway, then it’s questionable as to whether the taxpayer should be paying for that.”