A Jewish congressman has been backed by a Muslim politician in his fight to prohibit US cities from banning circumcision.

Brad Sherman, a Californian Democrat, is set to introduce a bill to counter the San Francisco campaign to make circumcision illegal for underage males.

Residents of the city will vote on that proposal in November, but Mr Sherman said such an issue was not in "the proper realm of cities".

He said his proposed "Religious and Parental Rights Defense Act of 2011 would allow Jews and Muslims to freely practise their religions.

He said: "Male circumcision has been practiced for thousands of years and is a deeply important ceremony for two major religions.

"Religious freedom is a federal issue, and medical practice is a state issue, maybe a federal issue as well." He added that while he would never want to make circumcision mandatory, the decision "should be left up to the parents".

Mr Sherman said the bill had already been co-sponsored by Keith Ellison, a Minnesota congressman who in 2006 became the first Muslim elected to the House of Representatives.