The US House of Representatives has voted 225-201 to sue President Barack Obama for exceeding his executive authority, launching an unprecedented legal challenge by a congressional body against a president.
Republican leaders say the lawsuit is intended to restore balance between the executive and legislative branches. They accuse the Obama administration of repeatedly circumventing congress to change existing laws.
Democrats call the suit a political stunt and say the president has resorted to using his executive powers because of congressional inaction and gridlock.
Wednesday's vote only reinforced the growing distrust between Democrats and Republicans, and became a partisan rallying cry for both parties.
The resolution approved by the House in a near-party-line vote authorises House Speaker John Boehner to file suit in federal court on behalf of the full body "to seek appropriate relief" for Obama's failure to enforce a provision of the Affordable Care Act
that would impose a penalty on businesses that did not offer basic health insurance to their employees.
That provision's effective date has been delayed twice by the administration and now won't fully take effect until 2016.
Even as it seeks to sue Obama now for failing to enforce the provision, the GOP-led House has voted several times to repeal the entire health law.
When he unveiled the suit, Boehner insisted it was about more than just Obama.
"If this president can get away with making his own laws, future presidents will have the ability to as well. The House has an obligation to stand up for the legislative branch," he said.
Democrats warned the suit could be the first step towards impeaching Obama. The latter point has become a staple of campaign messaging for Democrats as they seek to defy the historical trend in which a president's party loses seats in the mid-term of his second term.
The committee charged with electing more Democrats to the House announced this week it has raised more than $US7 million ($A7.57 million) since the suit was announced.