Colorado Common Cause will hold a rally Sunday in Avon to protest a Vail Valley retreat this weekend set up by conservative political donors Charles and David Koch.

The Koch brothers, owners of the Wichita, Kansas-based energy conglomerate Koch Industries, fund numerous right-wing causes and candidates and have spent millions seeking to roll back environmental protections and strip away regulations for the energy and mining sectors.

Colorado Common Cause today issued a release saying it will join with labor organizations and other progressive groups to “protest against oil/corporate billionaires Charles and David Koch’s efforts to control the nation’s future by spending hundreds of millions of dollars in secret money” on campaign ads.

The protest is set for 11 a.m. to 1 p.m. Sunday by the lake in Avon’s Nottingham Park. There has been no official confirmation that the twice-a-year Koch retreat will be held this weekend at the Ritz-Carlton, Bachelor Gulch – which recently went into foreclosure protection — or whether it will be held at some other Vail Valley location. Several websites have reported the event will be at the Ritz.

Common Cause, however, seems fairly certain the event will at least be in the Vail area, planning its protest in Avon “because American voters deserve to know who is behind the ugly political ads.” Avon is 10 miles to the west of Vail at the base of gated Beaver Creek Resort, which hosts the annual AEI World Forum conservative think tank.

On Wednesday, Virginia Gov. Bob McDonnell released his schedule, which said he would be attending the Koch seminar Sunday in the Vail area. Last year the Kochs held a retreat at the St. Regis in Aspen.