Image copyright Getty Images Image caption Patrick Conroy has served as House chaplain for seven years

More than 70 US lawmakers have demanded House of Representatives Speaker Paul Ryan explain why he fired the chamber's chaplain.

Catholic Reverend Patrick Conroy, who has served in the post for seven years, is the first House chaplain to be forced out.

The Jesuit said he may have lost his job because of a prayer.

Fr Conroy delivered the sermon last November, when lawmakers were debating legislation to overhaul the tax code.

"May all members be mindful that the institutions and structures of our great nation," he said, "guarantee the opportunities that have allowed some to achieve great success, while others continue to struggle.

"May their efforts these days guarantee that there are not winners and losers under new tax laws, but benefits balanced and shared by all Americans."

Image copyright Getty Images Image caption Fr Conroy (centre) led a prayer one day after a shooting at a congressional softball practice

About a week later, Fr Conroy said he was told by Mr Ryan's office that the top Republican was unhappy with the prayer.

He told the New York Times that the House speaker had told him: "Padre, you just got to stay out of politics."

In his letter of resignation on April 16, Fr Conroy noted that Mr Ryan had asked him to stand down, but says he was not given a reason.

House Democratic Caucus Chairman Joe Crowley called Mr Ryan's actions "reprehensible", and accused him of "pandering to anti-Catholic sentiment" from Republicans.

Mr Ryan, who is himself a Catholic, announced earlier this month that he will not run for re-election in 2018.

US House Speaker Paul Ryan to stand down

"The speaker is a proud, deeply Catholic person and this charge is not only false but outrageous," his spokeswoman, AshLee Strong, said in a statement.

"The speaker did a very bad thing," said House Democratic Minority Leader Nancy Pelosi.

Republican Walter Jones, who also signed the letter, said he was "very upset" about the chaplain's departure.

"If this is true about the prayer, and we have freedom of religion in America, how about freedom of religion on the floor of the House?"

On Friday afternoon, the House voted against a resolution to set up a select committee to investigate the chaplain's dismissal.

Speaker John Boehner named Fr Conroy as the first Jesuit priest to lead the House in 2011.