Team London, the Mayor of London’s volunteering programme, will launch a website on 30 May to help match people in the capital with volunteering opportunities.
Speaking at a Team London event this week, Patrick Feehily, interim assistant director at the programme, said charities that wanted volunteers should register with the site.
"It should enhance your profile," he said. "Organisations that sign up will be eligible for Team London funding and access to Team London volunteers."
He said the idea behind the website was "stolen" from the Cities of Service model introduced in New York City by its mayor, Michael Bloomberg.
Feehily said the Team London website would give Londoners access to volunteering opportunities in seven areas, including training and skills, greening and cleaning, and London events.
The site will allow volunteers to apply for opportunities with charities that are registered with the site, without having to go to those organisations' own sites, said Feehily. It is free for charities to register.
He said that because volunteers were able to create individual profiles, the website would enable Team London to capture information about "the impact of what these volunteers do".
Speaking at the same event, Diahann Billings-Burford, chief service officer of New York City Service, said that since its launch in 2009 the NYC Service website had attracted more than 1.2 million unique users.
She said the site supported 22 initiatives across New York, involving 575 organisations, and offered 771 opportunities to volunteers.
"We think that it is a really efficient way for volunteers and organisations to connect," she said.
As well as launching the site, Team London aims to appoint 1,000 London ambassadors to welcome people to the city during the summer months.There will also be opportunities for volunteers to help out at major sporting events in the city, such as RideLondon, and Team London aims to place a London ambassador in every school in the city, said Feehily.