The group of eight organisations, including The Scout Association, and UK Youth, has written an open letter to the main political parties ahead of the general election, arguing that action is needed as young people are finding it tougher to access housing, work and education opportunities.
They are calling for election manifesto pledges to include a commitment to providing a universally accessible, high-quality youth service. They also want provision of mentoring support from "positive adult role models", readily available information, advice and guidance services.
Politicians are also being urged to prioritise volunteering, paid internship, training and employment opportunities for young people. In addition, the group wants parties need to have a strong focus on developing life skills as young people make the transition into adulthood.
"This election offers an opportunity to accelerate social mobility, address social inequality and allow all young people to develop the social capital they need to thrive," the letter states.
"Social mobility is an issue that's been growing since the 1990s and as social divides become increasingly exposed, it's arguably one of the most important and challenging issues facing British society today.
"As we enter a period of unknown, the global economy and technology are changing at an incomparable pace, tearing up assumptions of what it takes to succeed along the way," the letter adds.
The group cites the Social Mobility Commission's State of the Nation report, published in November, as evidence of worsening social mobility issues facing young people.
The report highlighted a growing geographic social mobility divide with young people in rural areas and towns across the UK having less opportunities than those in the affluent London and the south east.
The letter adds: "Millennials may be the first to earn less than previous generations; home ownership among young people has halved in 20 years; only one in eight children from low-income backgrounds is likely to become a high-income earner as an adult; if current trends continue, nine million low-skilled people could be chasing the same four million jobs, while at the other end of the labour market there will be a shortage of three million workers to fill 15 million high-skilled jobs by 2022."
Anna Smee, chief executive of UK Youth, said: "Social mobility is one of the biggest issues of our time. Sadly, we still live in a society that grants success based on an individual's background, birth and location rather than their aspiration or ability.
"We hope all party leaders hear our call to accelerate social mobility and address social inequality to allow all young people, regardless of background or circumstance, to reach their potential."
The open letter has also been signed by: Girlguiding, Ambition, Leap Confronting Conflict, National Youth Agency, The Mix, and vinspired.