COAP had an income of more than £66,000 and spent just over £60,000 in the financial year ending September 2013. Action on Addiction had an income of £7.6m and spent £7.4m for the financial year ending March 2014.
A spokeswoman for Action on Addiction said in a statement that Emma Spiegler, COAP's founding director and only full-time staff member, would be retained as part of the agreement. The rest of the charity’s team were consultants and would also be staying on, the spokeswoman said.
COAP will retain its name, but its trustee board has stepped down as part of the merger. There will be no job losses at Action on Addiction.
The spokeswoman for Action on Addiction said that COAP was joining forces with Action on Addiction to enable it to increase its impact and further improve its services by attracting larger amounts of funding. She said that the decision to merge was not "due to a drop in funding".
Nick Barton, chief executive of Action on Addiction, said in a statement: "We are delighted to welcome COAP to the Action on Addiction fold. The online service will enhance the reach of our support for children and young people affected by parental addictions and will complement our Moving Parents and Children Together programme. Supporting these children and young people is important in its own right, but it also makes a contribution to prevention."
COAP supports an online community for young people who have concerns about a family member's addiction.