WASHINGTON AP – A watchdog group says it will file a complaint with the Senate Ethics Committee asking lawmakers to investigate the circumstances surrounding an affair that Sen. John Ensign had with a campaign aide.

Ensign, R-Nev., acknowledged last week that he was involved in a sexual relationship from December 2007 through August 2008. The aide was identified by her attorney as Cindy Hampton, who had worked for two Ensign political groups.