C J Doyle, of the Catholic Action League of Massachusetts, said: "It's an example of depraved morals and contempt for the sensibility of Catholics everywhere."
The key fobs, sold by Planned Parenthood of Connecticut for $3 via its website (http://www.ppct.org/), come in 28 designs including an image of a US flag with the stars replaced with the words "Wear with Pride" and a Statue of Liberty holding a condom instead of a torch.
Another reads "Condoms are cheaper than diapers" over a cartoon of a screaming baby.
Judy Tabar, Planned Parenthood of Connecticut's president and chief executive, said controversy over the key fobs had sparked a surge in traffic to its website this week.
She said 100,000 visitors swamped the site on Thursday, causing it to shut down temporarily, after internet columnist Matt Drudge posted a statement by a conservative Christian group condemning the key fobs as "blasphemous".
The key fobs had been on sale for a year, but had attracted controversy only this week.
"The media attention led to an avalanche of orders so much so that it caused our website to shut down. We have expanded our capacity and it is up again today," she said.
The politically sensitive issues of unwanted pregnancy and abortion are among the hottest topics in Washington this week during Senate confirmation hearings for Samuel Alito, the US Supreme Court nominee.
Kristian Mineau, president of the conservative Massachusetts Family Institute, called the Michelangelo detail "a very crude and crass manoeuvre".
"Condoms are the best protection against unintended pregnancy and infection, so it's really important to get the message out there"
Judy Tabar, Planned Parenthood of Connecticut's president and chief executive
"This does nothing to deal with the horrific promiscuity rate we have among teenagers," he said.
Taber said the variety of designs was aimed at appealing to a wide range of personalities.
"Condoms are the best protection against unintended pregnancy and infection, so it's really important to get the message out there," she said.