The United Nations Refugee Agency (UNHCR) has called on Germany to allow family reunions for all refugees, as the issue threatens Chancellor Angela Merkel's plans to forge a new government.

Restrictions introduced by Merkel's conservative-led coalition following the 2015 refugee crisis and aimed at trying to stem the demand for family reunions made no sense, Roland Bank of UNHCR Germany told a federal parliamentary committee hearing.

About four months after last September's inconclusive national election, Merkel hopes to sign off on a new coalition deal early next month with the center-left Social Democrats (SPD). But while the SPD believes that the right to family reunions should be extended to all refugees, Merkel's Christian Democrats (CDU) and their Bavarian-based Christian Social Union (CSU) allies are opposed. As a consequence, the issue has turned into a major stumbling block in the coalition talks.

The battle over family reunions has been further complicated by the prospects of elections in Bavaria later this year where the CSU is facing a tough challenge from the right-wing populist Alternative for Germany (AfD).

Under the rules introduced by Merkel's conservative led-government in March 2016, a large number of refugees from Syria and other war zones in the Middle East and Africa were granted a limited form of asylum known as "subsidiary protection".

In addition, Berlin decided that family reunions for this group would be suspended until March this year.

In a draft coalition deal earlier this month, Merkel and the SPD agreed to limit family reunions for refugees to 1,000 a month, but the status of this agreement and the potential for changes has been hotly debated since then.

But Hendrik Cremer from the German Institute for Human Rights warned that "those affected faced a constant risk of break downs" because of the lasting separation from their families. This is particularly the case as it is unlikely that many of the refugees will be able to return to their homelands in the near future.

However, Dieter Amann, an AfD lawmaker dismissed the concerns of the refugees, referring to what he said was the "continuation of the system of lying associated with asylum." Male refugees should not be allowed to bring over their families, but should return to their home countries, said Amann.