WASHINGTON — It is an unwritten rule that if a former Treasury secretary has nothing nice to say about one of his successors he does not say anything at all. But in the nation’s capital these days, the rules of political comity are meant to be broken.

Raising eyebrows in economic circles, Lawrence H. Summers, the mercurial Treasury secretary for President Bill Clinton, has leveled a barrage of increasingly personal criticism at the current Treasury secretary, Steven Mnuchin.

In podcasts, blog posts, op-eds and on Twitter, Mr. Summers, the former president of Harvard and a top economic adviser to President Barack Obama, has accused Mr. Mnuchin of damaging the credibility of Treasury by making “irresponsible” economic assessments of the administration’s tax plan and acting as a “sycophant” to President Trump.

The attacks have alternately amused and angered those who run in economic circles, with some saying it is Mr. Summers who is damaging the credibility of the office by leveling public attacks on a sitting Treasury secretary.