CHICAGO (CBS) — Explosive allegations made by the head of Chicago’s Fraternal Order of Police have triggered some in the union to call for his resignation.

The intramural fight in the FOP comes in the context of the start of campaigning for union officer elections in March.

This week, FOP President Mike Shields called for an investigation into allegations that contracts decided by an independent arbitrator before Shields became president in 2011 were fixed — decided in backroom deals between the city and former union bosses.

That has led to calls for Shields’ resignation.

UPDATE: Shields Suspended By State FOP

Chicago FOP field representative Saul Del Rivero said Shields’ allegations are “patently false” and “have no basis in fact.”

“Listen, we’re Chicago police officers. We deal in facts; not fiction, not allegations based without evidence, statements, something that would show us this actually took place,” he said.

Many believe Shields’ allegations were an attempt to cover up his own big mistake: failing to notify the city last year between Feb. 1 and March 1 that the union planned to terminate its contract with the city, and start negotiations on a new deal. That meant the old contract rolled over for another year, and the city was able to deny police officers an automatic retroactive pay raise. Instead, they’d have to give something up to get the pay bump.

Tracy Quarles, a 19-year veteran officer, has begun a petition drive calling for Shields to step down.

“We feel that we have been betrayed by our current FOP president, so many of us are here tonight to ask him to resign, or step down, and let someone come in and do this job and keep a watchful eye over the men and women who keep a watchful eye over this city,” he said.

Many in the FOP believe Shields bombshells are attempts to cover his biggest mistake which could cost police officers money in a retroactive pay raise.

FOP officer elections are in March…and campaigning is expected to begin next week.

An attempt was made to get reaction from Shields but his office says he’s taken a vacation day.