Liberia’s justice minister has resigned, complaining that she was barred from investigating the country’s main spy agency, run by the son of President Ellen Johnson Sirleaf.

In a letter full of dramatic language but short on detail, Tah claimed her job had become “unbearable” since she had noticed a “determination to systemically undermine and gut the portfolio of relevance and effectiveness”. She did not single out any individual for criticism or give further examples of how she had been undermined in her work.

Tah, who was also the government’s main legal adviser in her role as attorney general, says she offered to resign in March but was turned down and did not raise the issue again because of the Ebola epidemic.

The president’s office made no comment on Tah’s statement other than to confirm her resignation had been accepted.