The recommendation is among seven put forward in a report from the London Enterprise Panel, London Councils and the Mayor of London's Office.
The report states that every Londoner should have received their 100 hours of experience, in some form, by the time they reach the age of 16.
It suggests that lessons learnt and experiences gained over this period should be recorded in a "personalised digital portfolio".
The report states: "(The 100 hours) may include career insights from industry experts, work tasters, coaching, mentoring, enterprise activities, part-time work, participation in Skills London and The Big Bang Fair, work shadowing, work experience/supported work experience and other relevant activities."
The idea has been welcomed by school leaders who said there is "widespread agreement" that learning about careers and work needs to begin at primary school.
The report, entitled London Ambitions: Shaping a successful careers offer for all young Londoners, was launched last week by London mayor Boris Johnson.
There are expected to be nine million people living in London by 2021 and a quarter of the city's population is aged 19 and under.
More than 100,000 young Londoners are not in education, employment or training, while the 18 to 24 year-old employment rate is 53.8 per cent, compared with a UK average of 61 per cent.
Other suggestions in the report include calling on secondary schools and colleges to have an "explicitly publicised" careers policy and careers curriculum, including links with business, careers provision and destination outcomes.
It also underlines the importance of giving schools access to "up-to-date, user-friendly labour market intelligence/information", and it says that the quality of careers provision should be strengthened by developing "careers clusters" to share resources in improving awareness of the labour market.
Kathryn James, deputy general secretary of the National Association of Head Teachers, welcomed the report: "Learning about the world of work needs to start at primary school. Waiting until secondary is too late. While there is widespread agreement on this, there's little formal support from government yet."
The report comes alongside the development of the "London Ambitions Portal", which is aimed at helping schools to more easily find high-quality careers provision by streamlining initiatives, campaigns and services.
London Ambitions is backed by money from the European Social Fund, including £14 million focused on developing high-quality careers and jobs market advice across the capital, £13 million to develop youth talent, and more than £45 million targeting those not in education, employment or training.
For more information about the London Ambitions programme, visit www.london.gov.uk/priorities/schools-and-education/for-teachers/london-ambition