The Republican Party of Delaware filed a complaint Thursday with the Federal Election Commission (FEC) alleging illegal coordination between the Tea Party Express and the Senate campaign of Christine O'Donnell. 

O'Donnell is challenging Rep. Mike Castle (R-Del.) in the state's Republican Senate primary, set for next Tuesday. 

The Tea Party Express has been running radio and TV ads supporting O'Donnell, and the complaint alleges the group has coordinated with the O'Donnell campaign on its paid communications in violation of federal election law. 

The complaint cites an appearance by O'Donnell at a Tea Party Express rally and a radiothon that the group is planning for the candidate. O'Donnell is expected to speak during that event as well. 

The complaint also accuses the O'Donnell campaign of accepting contributions from the Tea Party Express is excess of legal limits. 

"Christine O'Donnell needs to immediately call upon her third party supporters to cease and desist this illegal behavior," Delaware GOP Chairman Tom Ross said in a statement. "This type of behavior has no place in our political process, and O'Donnell should denounce these illegal ads."

The state Republican Party has asked the FEC to expedite the case. An FEC spokesperson wouldn't comment directly on the complaint but suggested action on the matter before Tuesday's primary "would be a very quick turnaround."

No official response yet from the Tea Party Express or the O'Donnell campaign.