A statement from the two umbrella organisations said a meeting of the chairs, vice-chairs and chief executives of the bodies last week decided to coordinate several existing projects to promote the positive role of the sector in society and to develop new initiatives.
Paul Farmer and Martyn Lewis, the chairs of Acevo and the NCVO respectively, said in a joint statement: "The members of both our organisations have been telling us that they would like us to work together to make the case for a strong charity sector, especially with the risk of some negative stories about charities unfairly affecting the sector as a whole."
A spokesman for Acevo said that one of the projects the group would coordinate would involve speaking to editors of publications to try to improve their understanding of how the sector works.
The Understanding Charities Group, an initiative led by the NCVO and CharityComms, the membership network for communications professionals in charities, already had a plan in place to interview journalists to try to understand why the sector received low levels of generic coverage, according to a strategy document seen by Third Sector.
"This is simply to add greater weight and momentum to initiatives already in place and examine what other initiatives might be put in place to push forward a more positive message about charities," a spokesman for Acevo said.
He said the bodies would work with the Understanding Charities Group, which was set up last year to secure better treatment for charities in the media, to help it make suggestions to journalists for programmes or articles that could include charity coverage. The bodies did not intend to duplicate the group’s activities or "steal its thunder", he said.
The spokesman said it had not yet been decided what new initiatives the bodies would undertake.
Sir Stuart Etherington, chief executive of the NCVO, and Sir Stephen Bubb, chief executive of Acevo, are understood to be meeting on Thursday to flesh out the plan in more detail.
Responding to the announcement, the Understanding Charities Group steering committee said in a statement that it welcomed the move.
"We’ll be sharing the work of the Understanding Charities Group to date," it said. "We look forward to hearing more detail and to shaping and informing this important work."
Asheem Singh, director of public policy at Acevo, told Third Sector in August that the Understanding Charities Group could not have been expected to take a proactive stance during the recent media attacks on charities because the group did not have the necessary connections or figurehead.
A spokeswoman for the NCVO said it had not yet been decided whether the small financial commitments the umbrella body received from several charities a year or two ago for it to carry out research on public trust, which it had been considering transferring to the Understanding Charities Group, would now be retained to facilitate the joint work on these projects instead.
"These were pledges, not cash," she said. "The NCVO is not holding any money and we will, of course, talk to the organisations concerned about whether those pledges still stand and how that funding can best be used to help restore public trust and confidence in charity."
In May, the NCVO said it was creating the new role of media network coordinator to help charities promote stories about their activities to the mainstream media and piggyback on the news agenda. But the body struggled to find a suitable candidate and in August the role was readvertised.
The NCVO’s spokeswoman declined to say whether the body had hired anyone to the post.