BERLIN, June 24 (Xinhua) -- The ongoing dispute over the refugee policy within Germany's ruling coalition undermines its majority, according to a latest poll released Sunday.

In the weekly survey of the pollster Emnid for the "Bild am Sonntag," the Chancellor Angela Merkel's Union Party loses two percentage points and only reaches 31 percent of support rate.

As the German Social Democratic Party (SPD) remains unchanged at 18 percent, the Union-SPD ruling coalition formed in March has only 49 percent of support rate in aggregate.

The coalition won 53.4 percent of votes in the federal elections in September, suffering a great loss compared to that of 2013 due to the rise of right-wing populism triggered by over 1 million refugees inflows.

Merkel's Christian Democratic Union (CDU) is now in a unprecedented dispute with its Bavarian sister party Christian Social Union (CSU), as Horst Seehofer, German Interior Minister and chairman of CSU, threatened to bypass Merkel and implement a tougher policy to asylum seekers and for border control.

The two parties avoided a showdown last week as Seehofer agreed to give Merkel two weeks to find a European solution on June 28-29 EU summit.

By contrast, the Alternative fuer Deutschland (AfD) gained one percentage point to 16 percent, the highest figure that the far-right anti-immigration party has ever achieved in the Emnid Sunday trend.

Germany, France, Italy and several other EU members states will hold a mini-summit on Sunday to discuss a European solution for refugee and migration issue ahead of the EU summit.