BERLIN (Reuters) - Divisions in German Chancellor Angela Merkel's conservative bloc have weakened public support for her "grand coalition" and pushed the anti-immigrant Alternative for Germany (AfD) party to its highest ratings, a poll published on Sunday showed.
The poll conducted by Emnid for the Bild am Sonntag newspaper showed Merkel's conservative bloc at 31 percent, down two percentage points from the previous poll.
Merkel's conservatives are embroiled in an internal dispute over whether to turn back migrants at the German border who have registered elsewhere in the European Union.
The issue has divided the longtime conservative allies and poses the most serious challenge yet to Merkel's leadership, raising questions about a possible collapse of her right-centre coalition a little more than 100 days after it took office.
Interior Minister Horst Seehofer, leader of the Bavarian Christian Social Union (CSU), preparing for regional elections in Bavaria in October, has threatened to defy Merkel's wishes and order police to turn back asylum seekers unless she secures a broader EU deal on distributing migrants more evenly.
The centre-left Social Democrats, junior partner in the ruling coalition, remained unchanged at 18 percent in the new poll.
The far-right AfD, by contrast, gained one percentage point to poll at 16 percent, its highest rating in an Emnid poll, the newspaper said.
Boris Pistorius, interior minister of the northern state of Lower Saxony, accused the Bavarian conservatives of exaggerating the extent of the migration problems and adopting AfD campaign slogans ahead of the Bavarian regional election.
"We don't have a mass stampede at the border at the moment," the Social Democratic (SPD) politician told the Bild am Sonntag newspaper. "Copying AfD slogans will only strengthen the right-wing populists."
Markus Soeder, a top CSU leader and Bavaria's premier, plans to carry out the electoral campaign in Bavaria without involving Merkel, a first in the 70-year history of the CSU, according to the Welt am Sonntag newspaper.
Soeder has invited Austrian Chancellor Sebastian Kurz, whose ruling coalition includes the far-right FPO party, to participate in Bavarian election events, the newspaper said.
Soeder told hundreds of supporters at a political event on Sunday that his party wanted a complete shift in Germany's migration policies, including better border protections.
Emnid asked 2,336 people between June 14-20 which party they would support if a national election occurred the following Sunday.
(Reporting by Andrea Shalal)