The Government has pledged an additional £30m to support the expansion, which will also enable children to talk through their problems with counsellors over the internet.
A two-week national TV advertising campaign by Saatchi & Saatchi will mark the start of the initiative.
The Child's Voice appeal is partly for funding to take on extra staff and volunteers. The NSPCC wants to reduce the level of calls received by its services for adults and children that it fails to answer. About a third of the 2.3 million calls received by ChildLine last year went unanswered.
The charity aims to recruit 600 more volunteers to work with the 1,200 who already staff its helplines. It also hopes to increase the number of paid staff working on the services from 87 to 117 by 2011, and intends to open two new call centres.