A former City Hall fundraiser convicted of taking part in a massive NYPD corruption scandal is appealing his four-year sentence — claiming he should have been allowed to call Mayor Bill de Blasio as a trial witness.

In newly filed court papers, Jeremy Reichberg’s lawyer John Meringolo argues that allowing jurors to hear testimony from turncoat pal Jona Rechnitz about de Blasio allegedly taking bribes — without hearing from the Mayor himself — confused the jury, leading to his client’s conviction on conspiracy and other charges.

Reichberg’s defense team tried to subpoena de Blasio as a trial witness, but that request was quashed by Manhattan federal court judge Gregory Woods.

“The district court abused its discretion in admitting Rechnitz’s testimony concerning his alleged interactions with Mayor Bill de Blasio, first because the credible evidence failed to establish that any crime had been committed, and second because any probative value of the testimony was far outweighed by its likelihood of confusing and inflaming the jury,” Meringolo wrote.

“Because the defense was unable to call de Blasio to testify, the defense could not erase the prejudice caused by Rechnitz’s speculative assertions,” the court papers read. “The notoriety of the alleged bribe recipient and the highly publicized nature of Rechnitz’s claims alone warranted enforcing the defense’s subpoena to de Blasio.”

Rechnitz, who is facing sentencing later this month, testified that he and Reichberg bought access to City Hall by donating more than $100,000 to de Blasio’s pet causes.

The mayor has aggressively denied the claims, and blasted Rechnitz as a “liar.”