SACRAMENTO, California (Reuters) - A prominent Democratic California state senator and gun-control advocate was indicted by a San Francisco grand jury on charges of corruption and conspiracy to traffic in firearms, according to court documents released on Friday.

Suspended California State Senator Leland Yee departs the U.S. courthouse following a hearing in San Francisco, California March 31, 2014. REUTERS/Robert Galbraith

The indictment adds to the troubles facing state Senator Leland Yee, who was arrested last week and criminally charged along with two dozen others in the same case. He has since been suspended with pay.

Yee, 65, is the third California state senator to face criminal charges this year in separate cases that have cost Democrats a cherished two-thirds legislative majority in an election year and prompted them to cancel a major fundraiser planned for this weekend.

Senate Democratic leader Darrell Steinberg, who has said that the charges against Yee “sickened” him, on Friday renewed calls for the senator to resign.

“Senator Steinberg renews his demand that Senator Yee resign, and resign now,” spokesman Rhys Williams said in an email to Reuters.

The party, which dominates both houses of the legislature and holds all statewide offices, effectively lost its two-thirds majority in the senate last month. Senators Ron Calderon and Roderick Wright were placed on paid leave of absence after Calderon was indicted on corruption charges and Wright was convicted of lying about living in the district he sought to represent. Both were later suspended with pay along with Yee.

“The people of California deserve elected officials who embody the highest levels of integrity,” said Republican senate leader Bob Huff, who pushed for suspending the three senators. “It is very troublesome that we have three separate Senators in one year convicted or charged with various felonies.”

In canceling a glittering fundraiser that was slated to begin on Friday at the picturesque Torrey Pines Golf Course overlooking the Pacific Ocean near San Diego, Democrats acknowledged “extraordinary breaches of the public trust” in the three cases.

“These are unprecedented times and they demand that we take a step back and take stock of how we all do the people’s business and balance it against the demands of running for office,” Steinberg and lawmaker Kevin de Leon said in a joint statement on Tuesday.

CASH AND WEAPONS

In a 31-page indictment that sharpens but does not materially change the allegations against Yee, he is charged with six counts of corruption and one count of conspiracy to traffic in firearms.

Last week, his lawyer said he planned to plead not guilty, but yesterday Yee hired a new attorney, who did not respond to a request for comment on Friday.

Among the allegations contained in the indictment is that the one-time San Francisco mayoral candidate accepted cash from an undercover FBI agent seeking to purchase illegal weapons.

The indictment says Yee and his campaign consultant, Keith Jackson, sought to enrich themselves and pay off debt from Yee’s failed mayoral campaign by accepting bribes, both in cash and by check, from undercover FBI agents.

In one instance, Yee wrote a letter on behalf of a technology company that an undercover FBI agent claimed to represent, and in another he helped an undercover FBI agent who said he was working to legalize marijuana in the state, the indictment says.

In the indictment, the two men are also accused of offering to help another undercover FBI agent to obtain illegal guns.

Yee was arrested along with more than two dozen others last week in a broad sweep of suspected organized crime and corruption activity in San Francisco. Among those charged in the indictment is Raymond “Shrimp Boy” Chow, a Chinatown figure who is accused of money laundering and conspiracy.

An indictment is likely to make it more difficult for Yee’s attorney to argue that the charges should be dismissed, because the process for fighting an indictment is different than the process for fighting a simple criminal charge.

Yee is scheduled to appear in San Francisco court next week to be arraigned on the charges, according to court documents. Each of the charges against him carries a maximum sentence of 20 years in prison, according to a press release issued Friday by the U.S. Attorney for the Northern District of California, whose office will be prosecuting the case.