The commission told Childwatch that it had to find new ways of fundraising and criticised its partnership with publishing company Yellow Partnership.
The trustees of the Hull-based charity, which provides counselling and holidays for vulnerable children, have also been told to reconsider the position of its chief executive, Lesley Verne.
Verne was criticised for running the charity from abroad with her partner, a former trustee who has now resigned as a result of the investigation.
The commission received a series of complaints from members of the public who had been contacted by Yellow Partnership on behalf of the charity.
Investigators ruled that the organisations displayed a 'lack of transparency' because the company failed to tell customers how much of their money was donated to Childwatch. Such solicitation statements are a requirement of the Charities Act.
Verne, who was still chief executive of Childwatch last week, told Third Sector that the charity had since taken action to comply with the report's recommendations, but she declined to say what new sources of funding the charity had in place, or to discuss the future.
Megan Pacey, director of policy and campaigns at the Institute of Fundraising, said that relying on a single source of income left charities financially vulnerable. "Charities should ensure that their income is sustainable - it's always best not to have all your eggs in one basket," she said.
Pacey added that charities tempted to sign commercial fundraising contracts should resist if they tied them in for long periods, and argued that it was good practice to seek legal advice.
"If the commercial participator doesn't take charity law seriously, you're not off to a good start," she said. "Remember that it's the charity's reputation that is on the line, not the commercial partner's."
The Institute of Fundraising advises charities to review contracts at least once a year and to carry out regular 'mystery shops' to gauge quality.