London accounts for a fifth of the UK economy and 15% of the country's jobs, a City of London report has suggested.
London's trade is as important as tax revenue, experts say
The study said London was "pivotal" to the health and success of the UK's economy, and pumped money and ideas into other regions of the country.
The study also founds immigrants make up one-third of London's workforce, most of them young, skilled workers.
It also showed tourism accounted for 6% of the capital's economy, and was set to rise ahead of the 2012 Olympics.
City of London policy chairman Michael Snyder said: "London's contribution to the rest of the UK is not just via tax revenues and public finances.
"London attracts the best and brightest workers from around the world, draws tourists to the UK and acts as a funnel for business and capital investment to regional areas."
He said: "The government, and the country as a whole, cannot afford to let London's growth falter.
"Investment in Crossrail is a major boon for the London economy and will create hundreds of jobs. Commitment to keeping London at the top of its game internationally is vital.
He said people and businesses from around the world wanted to do business in London but "aviation hubs, public transport, training opportunities and quality of life need to be top class if we are to compete on the world stage".
Dermot Finch, director of research group Centre for Cities, said: "There's no question that London is vital to the UK economy, but when talking about London and the rest of the UK, too much attention is being focused on London's tax contribution when the real story is about trade."
Recently, the head of market for the Notting Hill carnival suggested the event could raise £100m for the country, while the Olympics could generate £3bn from tourism alone.