GOP Senate challenger Mike McFadden's campaign said Sunday they were planning to file a complaint with the Federal Elections Commission Monday alleging Democratic Sen. Al Franken's campaign is illegally coordinating with a Super PAC.

At issue are two ads released roughly the same time that are similar in composition and message. One was launched and paid for by Franken's campaign, the other launched and paid for by Independence USA PAC, an outside group bankrolled by former New York City Mayor and billlionaire Michael Bloomberg.

Bloomberg, according to FEC reports, has invested $500,000 in television ads to support Franken.

It is against federal law for campaigns to coordinate with outside political groups.

"The similarities in these two ads go beyond coincidence," said McFadden's spokesman Tom Erickson. "On Monday we'll be filing a complaint with FEC alleging coordination between the Franken campaign and this super PAC."

Franken's campaign called the alleged complaint "desperate."

"This is a silly complaint by a desperate campaign trying to change the dynamic of a race," said Marc Elias, the campaign's lawyer.

McFadden's campaign is among two dozen campaigns already being investigated for illegal coordination after a complaint was filed in October by the American Democracy Legal Fund. The complaint alleges McFadden's camp, along with dozens of others, were illegally working with Koch-funded Americans for Prosperity, Crossroads GPS and a number of other Republican outside groups.