Image copyright Joshua Lott/Getty Images Image caption Steve King is known for his incendiary comments

Democrats are calling for a Republican congressman to resign after he defended abortion bans by saying that humankind might not exist but for rape or incest.

Without rape or incest "would there be any population of the world left?" nine-term lawmaker Steve King asked the Des Moines Register newspaper.

Mr King was defending anti-abortion legislation that does not make exceptions for rape or incest.

Democrats Kirsten Gillibrand and Bernie Sanders soon demanded he step down.

"You are a disgrace. Resign," Ms Gillibrand wrote on Twitter. Her remarks were quickly echoed by other 2020 Democratic hopefuls Cory Booker, Beto O'Rourke and Julián Castro.

A Republican lawmaker, Iowa state Senator Randy Feenstra, also criticised Mr King's remarks.

"I am 100% pro-life but Steve King's bizarre comments and behaviour diminish our message," he wrote on Twitter.

On Wednesday, Mr King told the Des Moines Register that the Republican leadership had stopped bills he sponsored banning abortions from advancing through the US House of Representatives.

"What if we went back through all the family trees and just pulled out anyone who was a product of rape or incest? Would there be any population of the world left if we did that?" Mr King said on Wednesday.

"Considering all the wars and all the rapes and pillages that happened throughout all these different nations, I know that I can't say that I was not a part of a product of that."

Business as usual

Steve King is no stranger to controversy. His remarks about race and immigration, as well as his ties to white nationalists across the globe, have essentially made him a persona non grata in the House of Representatives, including among his own Republican colleagues.

Outrage is frequently the baseline response when the nine-term Iowa congressman steps in front of a microphone.

Even when he's defending a view many anti-abortion activists hold - that rape and incest exceptions to abortion bans are immoral because they result in what they believe is the loss of innocent human life - he manages to do so in a way that grabs headlines and generates offence.

The days of marauding armies that rape and pillage are, mercifully, long gone in most of the world. And while it may be true that the descendants of those vile acts are alive today, it's a stretch to apply the atrocities of the past to a modern public policy debate.

At the very least, it appears deliberately inflammatory. In other words, it's business as usual for Steve King.

Mr King has earned a reputation for his incendiary comments. The Iowa congressman was already stripped of his committee assignments by his Republican colleagues in Congress last month, after the New York Times published an interview in which the congressman questioned how the phrases "white nationalism" and "white supremacy" had become offensive.

After he was disciplined, Mr King compared himself to Jesus Christ.

The Republican has made a number of remarks widely seen as racist and xenophobic, once tweeting his support for the Dutch anti-Islam politician Geert Wilders.

"Wilders understands that culture and demographics are our destiny," Mr King wrote on Twitter.

"We can't restore our civilisation with somebody else's babies," he added.

Mr King later defended his comments, saying on CNN that he "meant exactly what he said".

The lawmaker kicked off his bid for a tenth term in Congress in February and will face re-election in 2020.