Ed Miliband will put himself on the side of the "forgotten 50%" on Tuesday by drawing on his state school roots and promising to reform an education system that he says fails half of Britain's teenagers by giving them second-rate vocational qualifications of little value to employers.

In his address to the Labour party conference in Manchester, constructed around the theme of working together to rebuild Britain from recession, he will contrast his commitment to help those who don't go to university with a Tory plan for an education system designed "for a narrower and narrower elite".

He will also explicitly call on his party to shift focus from Tony Blair's earlier commitment to increase the numbers going to university towards helping the teenagers between 14 and 18 who are in need of good vocational education to keep them from dead-end jobs.

"We cannot succeed if we have an education system that only works for half the country. It's time now to focus on those who don't go to university," he will say.

Repeatedly drawing on his own experience at a London comprehensive – implicitly contrasting his own schooling with the Eton-educated David Cameron's – he will say that although for a quarter of a century children successful at exams have found the world open up, for the remainder school has offered very little and they have found themselves written off.

His schooling at Haverstock school in north London taught him "a lot more than just how to pass exams", he will say. "It taught people how to get on with each other, whoever they are and wherever they're from. I will always be grateful because I know I would not be standing here today as leader of the Labour party without my comprehensive school education."

He will try to explain why his roots are so different to Cameron's, saying: "My family has not sat under the same oak tree for the last 500 years. My parents came to Britain as immigrants, Jewish refugees from the Nazis. I would not be standing here today without the compassion and tolerance of our great country." Setting out plans for a clear vocational route to a gold standard qualification at 18 called a Technical Baccalaureate, he will also require all young people to study English and Maths to 18 as a strict condition for the award of the "Tech Baccs".

He will also propose a German style shakeup of post-18 apprenticeships, in which companies, on an industry or regional basis, can sign legally enforceable agreements requiring all participating firms to pay a levy to cover the cost of training, so – ending the scourge of freeloading companies refusing to pay the costs of apprenticeships, but stealing skilled staff from firms that do train.

He will also give businesses control of the £1bn budget of the Skills Agency.

Labour regards its plans for the forgotten 50% as far more sweeping than the tinkering reforms to A-levels proposed by the education secretary, Michael Gove.

The proposal for a Tech Bacc, which was supported by Miliband's industry adviser, Lord Adonis, originates from a report by Prof Alison Wolf in 2011 commissioned by Gove.

Wolf found: "The staple offer for between a quarter and a third of the post-16 cohort is a diet of low-level vocational qualifications, most of which have little to no labour market value. Among 16 to 19-year-olds, the review estimated that at least 350,000 got little to no benefit from the post-16 education system". The report highlighted that only 4% of 16-year-olds who have failed GCSE Maths and English go on to pass them by the age of 19, an omission that contrasts with the rest of the world's absolute determination to improve basic numeracy and literacy of its post-16 vocational students.

Gove welcomed the report, but has not implemented it, prompting Miliband to claim Gove has contempt for vocational qualifications.

More broadly Miliband will call for a society in which everyone can, and is expected to, play their part in restoring Britain. There will be calls on banks to work together with small firms and businesses to co-operate with long-term shareholders.

Conservative sources dismissed Miliband's reform initiative, saying Gove has already set out the goal Miliband is discussing, has already changed the funding system to begin this transition, and that Miliband's pledge will already have happened long before the election.

Miliband knows he faces a huge task to convince voters he is prime minister material, and much of the speech, some of it delivered away from the podium, will be designed to re-present himself to unimpressed voters.

His task was not made any easier by the frequently critical Blackley and Broughton MP Graham Stringer telling a fringe meeting in Manchester that Miliband had "failed to make a human connection with the electorate" and was "incapable of fighting the next election on personality".