Ed Miliband said addressing the national engineering skills shortage will be a key objective of his government if Labour wins election.
Speaking during a visit to the Crossrail construction site in central London, the Labour leader said his party will ensure there are 400,000 additional engineers in the UK by 2020.
"Our country faces a shortage of 400,000 skilled engineers if we don't act. That's why it's the mission of the next Labour government to put that right,” he said.
"It's the way we will create good jobs at decent wages and it's also the way that we are going to create a recovery that doesn't just work for a few people at the top but actually works for working people."
He acknowledged that an extremely low number of women among the UK engineering workforce was a major problem, saying the situation was an "embarrassment".
He called for a complex solution, stating the skill gap was a result of years of negligence.
"Over a long period we haven't taken the action necessary to get the skilled engineers we need," he said.
"That's about inspiring our young people in schools and colleges and creating new gold-standard technical qualifications for them in engineering.”
He said putting pressure on major engineering firms to create apprenticeship opportunities would be a key part of the strategy of the possible future Labour government.
"It's about saying to companies 'if you want a major government contract you must provide apprenticeships, if you bring in a skilled worker from outside the European Union you must also provide apprenticeships for the next generation',” he said.
Miliband’s visit to the Tottenham Court Road construction site comes amidst a difficult period in his leadership following the departure of the Islington South Labour MP Emily Thornberry from his shadow cabinet after her controversial tweet of an image of a house flying three St George flags with a white van parked outside.
During the visit Miliband toured the construction site, calling it "an inspiring place to be".
Later, he wrote on Facebook that any future government would have to choose between two directions for the UK – one through boosting the numbers of adequately-paid skilled workers, the other through "cowboy recruitment agencies, operating in the shadows of the economy, exploiting workers, undercutting wages and undermining conditions".
According to Labour, the UK industry will need about 780,000 new engineers by 2020 to satisfy the demand driven by investment into infrastructure and major engineering projects, including Crossrail.
However, according to projections, Labour said only about half that number will be trained by that time, leaving a considerable gap.
"This is not just a shortage of the traditional civil, mechanical and electrical engineers, but also in information technology, green energy, and life sciences where many of the jobs of the future will be created,” Miliband said.
"And we need to ensure Britain does not waste the talents of our young people, be they men or women.”
Miliband pledged to work closely with schools and industry to encourage the interest of school children in STEM subjects and make apprenticeships a viable career progression choice, equally valuable to going to university.