Some 300,000 members of Germany's second-biggest party submitted postal ballots Thursday to decided whether their party, the Social Democrats (SPD) will join forces with Chancellor Merkel's Christian Democrats (CDU), and sister party Christian Social Union (CSU) in a grand coalition.

While approval by the party is expected amid SPD leadership confidence that it will win a majority, there were fears that the unprecedented referendum would be flawed by members failing to follow all the voting guidelines.

Die Welt newspaper online said one-tenth of returned ballots were likely to be declared invalid because they were not accompanied by a legally binding affirmation that the member had not voted twice.

A grand coalition agreement was reached between the trio on November 27, after the CDU/CSU alliance narrowly failed to win an absolute majority in the September 22 general election.

Both the CDU and CSU have approved the deal. On Saturday, the SPD's youth wing voted at a conference in Nuremberg rejecting the deal, citing in particular the lack of a credible plan to finance investment in the future.

The final count is expected late Saturday.

Cabinet speculation

Ahead of the vote, the allocation of positions in the new cabinet have been kept under wraps.

Analysts believe Merkel is likely to distribute five ministries to those from her own CDU party, three to the CSU and six to the SPD.

Despite the secrecy, Sigmar Gabriel is widely expected to become economics and energy minister, with former foreign minister Frank-Walter Steinmeier tipped to return to the post if it is given to an SPD member.

hc/jr (AFP, dpa)