The Shelbourne Hotel has been given four weeks to explain why it removed four statues from outside the front of the building and answer allegations that the move breached planning laws.
Dublin City Council has issued a warning letter to the hotel, formally advising it that complaints have been made against it and that it is under investigation for breach of the law governing alterations to protected structures.
Under the Planning and Development Act 2000, no change can be made to a protected structure that would affect its character without prior planning approval.
The hotel did not seek either planning permission or a 'Section 57' declaration that the proposed alterations were minor enough to be exempt from the requirement to seek permission.
Up to yesterday, it had not submitted an application for retention of the changes it made either.
A spokeswoman for Dublin City Council said the investigation may take some time.
"Our planning staff will need to speak with the complainants and consider any submission the hotel may make within the four weeks, and then look at where things stand as regards the law before deciding the next move," she said.
The Irish Georgian Society and other conservationists complained after the sudden removal last month of four life-size bronze statues that had adorned the five-star hotel's entrance since 1867.
At the time, the hotel indicated it had taken down the statues in light of the Black Lives Matter movement, which has led to the removal or damaging of statues displayed in prominent places abroad because of their links with the slave trade.
The statues, which were designed and made in France, are of four women from ancient Africa, two of whom appeared to be shackled, but considerable debate has raged as to whether they actually depict slaves.
A copy of the catalogue from which they were ordered does not refer to them as slaves and the argument has been put forward that their supposed shackles are nothing more sinister than decorative anklets.
Other commentators have argued that regardless of whether or not they are slave girls, the statues have artistic merit and historical importance and should not have been removed. Anti-racism activists welcomed the move, saying the depiction of African women as slaves or colonial curiosities was offensive.
Senator and barrister Michael McDowell, who severely criticised the hotel's actions in the Seanad last week, revealed he had also lodged a formal complaint.
Dubbing the statues the 'Shelbourne four', Mr McDowell, who as justice minister, caused controversy over remarks about the 'Colombia Three', said he wanted the figures put back.
"I have lodged a complaint with Dublin City Council planning enforcement section calling for the Shelbourne four to be freed and reinstated," Mr McDowell tweeted.
Under the planning acts, Dublin City Council has powers to order the restoration of the statues if their removal is found to breach regulations.
If the matter was to escalate and proceed to court, a range of fines and penalties could apply, in addition to a restoration order.
If it is found that the hotel requires planning permission, any application it would make to Dublin City Council would be open to public observations and objections.
The hotel has previously gone through the planning process for alterations and extensions to the property, supplying the planners with lengthy expert reports on the historic architectural features.
It is not known what approach the hotel intends taking to try to resolve the issue.
No-one from management was available to comment and the parent company, Marriott, has also declined to respond to queries.