The arrangement, which will see Community Links join the Catch22 Group, means Community Links retains most of its independence, including keeping its current offices, chief executive and board.
Community Links will also benefit from access to Catch22’s back-office and group services support, a statement from the charities said.
But they said that some non-front-line job losses were possible in the future as part of a drive for back-office savings, although there were no definite figures for the number of jobs at risk or the likely savings to be made.
Catch22, which provides services including educational support, offender management and mentoring, has about 1,000 employees and an income of about £50m a year. Community Links has 48 employees and an annual income of almost £4m.
Chris Wright, chief executive of Catch22, will also sit on Community Links’ board as part of the new arrangement, and both charities will retain their separate charity numbers and brand identities.
Wright said he hoped the changes would mostly be completed by the end of Catch22’s financial year at the end of August.
He said the new arrangement would strengthen the work of both charities.
"I have long known of Community Links and have a huge regard for its work and how rooted its is in its community," said Wright.
"Community Links, being a well-established provider of a range of different kinds of community activity, provides a really strong foundation to explore new ways of delivering public services.
"This is a good time to do this, because maybe in two or three years it would be a less attractive proposition. But as it stands, there is a really strong foundation to build on, with some excellent and innovative practice."
Wright said the partnership with Community Links would be similar to the arrangement Catch22 had with Only Connect, which was taken over by Catch22 in 2015 and also retains an independent brand and management.
"We’d be shooting ourselves in the foot if we didn’t build on the heritage of Community Links," said Wright. "It’s an incredibly well-recognised and established organisation in east London.
"Our approach is to use the platform that Catch22 has created to give greater strength and support to community organisations such as Community Links. We don’t need to incorporate it into the Catch22 brand because I think that’s just about vanity. What’s really important is providing the access to our group structure and back office."
Arvinda Gohil, chief executive of Community Links, said the only way the charity could grow in the long term was through an arrangement such as the partnership with Catch22.
"Charities like ours have to find a way of continuing to work in the communities that we work in," she said.
"The operating context is incredibly challenging for charities like us, and this is a perfect way to come together in a partnership where we can carry on the work we have been doing for 40 years while building on the strength of the group partnership and building resilience locally."