The woman reportedly has 11,000 followers on her account and she acknowledged to the Neue Zürcher Zeitung that people in her workplace might have access to the photos.
The woman, reportedly a resident of Fribourg, told the NZZ she was aware of the concerns.
But she maintained that the postings are part of her private life and do not conflict with her job.
The woman has been suspended pending an internal investigation.
Her actions appear to conflict with the recommendation of the federal personnel office (EPA) that employees “only publish on the internet pictures and text that you would show at any time to your colleagues, employees or superiors”.
The NZZ said all the same it was not clear what the consequences of the secretary’s activities were.
The newspaper noted that the photos posted on the Twitter account clearly show her government office.
It reported the EPA saying that each administrative unit of the federal administration was responsible for implementing rules dealing with social media independently.
But the personnel office also noted the code of conduct for federal employees requires that they be careful even in private life “not to impair the reputation and prestige of the federal government”.
An ambassador or a government spokesman could not be permitted to engage in such behaviour, Thomas Geiser, a specialist in labour law at the University of Saint Gallen, told NZZ.
But Geiser said he believed the case warranted a warning more than a dismissal, provided the woman’s behaviour did not put the security of the institution or herself at risk.
Tabloid newspaper Blick, which published revealing photos of the secretary found on the internet, on Thursday reported online that the secretary had made 200 amateur porn films.
Many politicians told the daily they were unhappy with the revelations.
While arguments can be made about private life, "taxpayers may expect federal employees to work in the office rather than to post nude pictures of themselves," MP Natalie Rickli, a member of the right-wing Swiss People's Party, is quoted as saying.