More than 100 active investigations into NI charities
The Charity Commission is trying to deal with a backlog of more than 100 active investigations in Northern Ireland.
The longest running probe is almost five years old, dating to 2014.
The regulator said delays were due to the high number of complaints here and "low levels of staff resourcing".
It added that combination means it is "not always able to deal with concerns as quickly as the public might expect".
The revelation comes amidst general backlogs affecting a wide range of the work carried out by the Commission.
In December, BBC News NI reported on how almost 100 Parent Teacher Associations (PTAs) across Northern Ireland are waiting to be registered as charities, affecting their ability to apply for certain funding.
A spokeswoman for the watchdog told BBC News NI: "Given the high volume of enquiries, related queries and concerns received, the Commission does not currently have the resources to progress investigations into more minor concerns, instead focusing scarce enquiries' resources on the issues of highest risk to a charity's beneficiaries and assets."
The statistics on investigations were released in response to a Freedom of Information request from BBC News NI, although the names of charities involved have been withheld.
Terrorism and sexual harassment claims
In the six years from January 2013, the Commission has investigated and closed just over 560 complaints.
That number splits almost equally between concerns which were substantiated and those which were not.
A total of 116 complaints remain under active investigation, with 10 of those more than three years old.
Just over half relate to accusations made in the past 12 months.
The most serious outstanding complaints include claims that a charity's premises and funds are being used to plan and finance terrorism.
There are also allegations of a decades-old complaint of sexual harassment, missing money, the alleged overpayment of £7,000 in travel expenses to a chief executive and concerns over safeguarding issues.
The total number relates to all issues logged, and does not distinguish if multiple complaints have been made against the same charity.
Majority given regulatory guidance
Of the cases which have been closed, many did not involve the Commission taking action, although in certain circumstances a concern was referred to another agency such as the PSNI.
The figures show that in the majority of cases in which Commission did follow-up concerns, it took the form of a 'self-regulatory enquiry', whereby the regulator works with the charity to address issues by offering advice or guidance.
Other options include making recommendations and proposing a timeline for implementation, which happened in around 30 instances.
In six cases, there were found to be more serious breaches of charity law.
Two of those led to the publication of official reports by the Commission, with a report pending in a third case.
In the remaining three cases, one charity went into liquidation while the regulator concluded that two other charities had adequately responded to guidance given.
Some of the cases demonstrate the obstacles faced by the Commission in pursuing charities accused of wrongdoing.
In one example in 2014, the watchdog said it had been "ultimately frustrated in establishing whether charitable assets were appropriately disposed of" in the case of a charity which had closed and was accused of not paying a supplier, but added that it would pass information to the PSNI.
Other guidance given included rules surrounding the endorsement of political parties.
In April 2016, the Commission issued advice to a charity which "used its Facebook page to promote a candidate in the upcoming elections".
Complainants have expressed frustration at delays, with one telling BBC News NI they had not received any updates on concerns raised 18 months ago.
Investigations "may take some time"
In a response to a complainant last year, the Commission said it "does not provide updates on the progress of concerns" but added "a concern may take some time to investigate....however, at the end of the process you will be advised of the outcome of the investigation."
A spokeswoman for the Charity Commission told BBC News NI: "A concern may take some time to investigate, depending on how complex the case is, what evidence is available and what risk there is to the charity's assets or beneficiaries.
"Some concerns may also involve other regulatory bodies, for example a concern may remain open while the Commission awaits the results of investigations by other bodies, such as the PSNI, which can further lengthen the process."