Studies by the Organisation for Economic Co-operation and Development pinpoint expensive failures in most of the member countries which embarked on such schemes since the late 1970s. But the UK is one of the worst.
Norman Bowers, who heads the OECD's employment analysis and policy division, said that the soaring jobless rates had occurred "despite the huge proliferation of youth employment programmes in Sweden and the UK. In fact, unemployment rates worsened everywhere." He added: "The only exceptions are Ireland and Germany."
Schemes are failing to give young people the long-term, flexible skills needed to cope with the shift from manufacturing to service industries.
Countries best able to deal with the rising youth jobless levels were those which maintained strong apprenticeship schemes and developed a tradition of "social partnership" between employers, government and trade unions, Mr Bowers said.
He was speaking at a careers convention held last week in Ireland organised by the Training and Employment Authority. More than 100,000 students sampled the careers options on offer from more than 200 private and public-sector employers.
The convention, Opportunities 99, was created partly to tackle the skills issues identified by Norman Bowers. He warned countries against looking for simple solutions from others employment and apprenticeship policies but said all needed to act urgently.
"If young people do not get integrated into the labour market and have decent wage growth, we have the possibility of part of our youth being a lost generation, marginalised and lacking social cohesion."
One in four school-leavers in OECD countries was unable to find a job, despite declining populations and falling wage rates compared with adults. "OECD optimism of 20 years ago has turned to pessimism," he said.
It was misleading, he added, to look at the proliferation of part-time and temporary jobs. In Germany, 62.8 per cent of young people were in temporary work, compared with 27.3 per cent in the UK. "In Germany, well above average numbers are going into temporary jobs but they are jobs with training and are part of the dual (apprenticeship) system.
Despite the UK job training measures through the 1980s and 90s, employment rates among young people aged 16 to 29 worsened from 75 to 68 per cent. Labour's New Deal and the Modern Apprenticeship must offer real and lasting skills for all recruits to such programmes, he said.