Washington, July 7 (DPA) The Obama administration filed a lawsuit Tuesday against the state of Arizona over a controversial immigration law that has sparked widespread protests across the country.

The US Justice Department filed the lawsuit in a district court in Phoenix, arguing the state of Arizona had infringed upon the federal government's right to dictate immigration policy. Arizona politicians argue it was federal inaction that forced them to adopt the law.

The federal government argues in its filing that the Constitution and federal law do not permit the development of a patchwork of state and local immigration policies throughout the country.

It also requested that the law, which is set to go into effect at the end of the month, be suspended until the court could rule on the matter.

The controversial law requires police to request immigration papers during regular traffic stops and other interactions. Critics say the law, considered the toughest in the country, will lead to racial profiling.

Arizona Governor Jan Brewer said on Twitter before the suit was filed that the state would "be very aggressive in defending our law".

Police have criticised the law as being unenforceable - a view shared by President Barack Obama - and others see it as simply racist, even while residents in the southern border state have shown broad support for the measure in order to curb the flow of illegal immigrants through the state.

In a speech calling for immigration reforms last week, Obama said the Arizona law "ill conceived" but also a result of states taking the issue into "their own hands" because the federal government has failed to act.