Bishop Michael Sheridan's pronouncement was the strongest yet from a U.S. bishop in the debate over how faith should influence Catholics in this election year.
The discussion of withholding Holy Communion had previously been limited to politicians themselves.
Sheridan made his remarks in a May 1 pastoral letter published in the diocese's newspaper. He said he singled out abortion, stem-cell research, euthanasia and gay marriage for criticism because they are "intrinsically evil."
"It is primarily the legislator who enacts it of course," Sheridan told CBS News Correspondent Jim Axelrod. "But next down that chain is the voter who put the legislator in office."
When the idea was raised Easter week that Democratic presidential candidate John Kerry might be denied communion for supporting abortion rights, Sheridan was quick to draw the battle lines.
"We have separation of church and state in this country and people need to remember that. That's how we are defined as a nation," Kerry said at the time.
Sheridan says that simply means there can be no state religion and insists that Catholics are required not to vote for anyone who veers from church teaching, reports Axelrod.
Sheridan's letter was sent to each parish in the diocese, including 125,000 Catholics in 10 counties.
Formal Vatican pronouncements last year specified Catholic politicians' duty to uphold church teaching as they set policy on matters such as abortion and preventing the legalization of same-sex unions.
Last month, Cardinal Francis Arinze said a Catholic politician who supports abortion rights "is not fit" to receive the Eucharist. The debate was spurred by Catholic presidential candidate John Kerry's support of abortion rights.
Sheridan said some Catholics have challenged him to extend his list of positions out of step with church teaching to include the death penalty or the war with Iraq. But Sheridan said he doesn't believe those matters carry the same weight.
Denver District Attorney Bill Ritter, a Catholic, criticized Sheridan's letter.
"I just think this is a tragic direction for the bishop to take," Ritter said. "My great fear is that it will drive Catholics away from the church, Catholics who abide by the church teaching in everything they do but look at candidates and vote on a range of issues."