Tensions over immigration reform flared into the open Tuesday as the White House and House Republicans exchanged rhetorical barbs over the GOP’s commitment to an issue central to President Obama’s agenda.

White House press secretary Jay Carney criticized as “laughable” a claim by Speaker John Boehner (R-Ohio) that nobody had done more than him to fix the nation’s immigration system.

The House Republican chairman of the immigration subcommittee, meanwhile, attacked White House senior adviser Dan Pfeiffer as a “demagogic, self-serving political hack” for his criticism of an emerging GOP proposal.

The back-and-forth marked a departure from the careful tone that both the White House and Republican leaders had adopted on immigration in recent months, with Democrats growing increasingly impatient with the House’s slow-moving, piecemeal approach to the issue.