Suspended South African Revenue Service (Sars) head Tom Moyane has threatened legal action over his suspension. 

In a letter that Moyane wrote to President Cyril Ramaphosa on March 19, he said that his suspension was part of an "unlawful process". 

The letter, which appears to have been sent before his suspension was communicated to the press late on Monday evening, states that if Ramaphosa were to go ahead and suspend him, he would seek a court interdict. 

When contacted for comment by Fin24 on Tuesday morning about the possibility of his legal action, Moyane said he could not comment. 

He also did not comment when asked whether he thought his suspension was unfair. 

In a late-night statement on Monday evening, the Presidency announced that Moyane had been suspended with "immediate effect" pending the institution of disciplinary proceedings.

"President Ramaphosa said [the suspension] was in the public interest to restore the credibility of Sars without delay," said Presidency spokesperson Khusela Diko on Monday evening in a statement.

"In a letter to Mr Moyane, President Ramaphosa said 'Developments at the Sars under your leadership have resulted in a deterioration in public confidence in the institution and in public finances being compromised. For the sake of the country and the economy, this situation cannot be allowed to continue, or to worsen,'" said Diko.

Mark Kingon has in the meantime been appointed to head Sars in an acting capacity.