The team was first set up 18 months ago and initially comprised three people. It has since grown to nine.
The team, which produces all the charity's literature except its direct mail, hopes to save more than £500,000 this year and to increase this to £1m a year eventually.
Ian MacArthur, creative director at the NSPCC, says: "Initially, each team member had to pay for themselves twice over. Although the amount saved per head is less as the team expands, it's still a significant saving."
Like many charities, the NSPCC used to rely on external agencies to design all its literature, which was not only expensive but also led to inconsistencies in the charity's message. MacArthur says. "It's difficult for outside agencies to get under the skin of the charity - so, although some great design work was being produced, it sometimes looked like our logo had just been stuck on the bottom as an afterthought. It meant some of our work was being undermined inadvertently.
"With an in-house team, we have people who have got the chance to live and breathe the relevant issues."
Although having an in-house design team might seem like an impossible dream to smaller charities, Macarthur argues that it makes financial sense.
"Some smaller organisations spend about £20,000 just on producing their annual review," he says. "Someone can do that in-house and work on a couple of other projects and they will pay for themselves.
"A lot of charities are nervous about taking on members of staff when they are unsure about how much work there will be for them, but if you look at the money they are spending on design, the decision justifies it."
The NSPCC is not the only charity to have a design team on site: Barnardo's has had one for more than 25 years. Ted Trott, studio manager at the charity, says: "The team gets through a massive amount of work - about 700 jobs a year. An outside agency would kill for that amount of work, but it would cost a fortune. It's much cheaper this way, and we can make sure quality standards are consistent."