BERLIN: German Chancellor Angela Merkel's coalition partners Sunday chose a former economy minister as their candidate in national elections in September, as the party battles for its political survival.

The pro-business Free Democrats (FDP), which has governed with Merkel's conservative Christian Democratic Union since 2009, selected Rainer Bruederle, 67, to represent them in the September 22 vote in Europe' top economy.

"People want a strong voice for freedom. The chance is there for us. We should use it and we want to use it," said Bruederle during a 75-minute speech at the party conference in Berlin.

"I know you will all fight with me," he told the 600 delegates, who responded by giving him a five-minute standing ovation.

"Let's go into battle," he shouted, to cheers and applause.

Bruederle has a tough scrap ahead of him, as the party struggles to turn around its fortunes following years of internal bickering and plunging support.

With now Foreign Minister Guido Westerwelle as candidate, the FDP was the surprise package in the 2009 elections, polling 14.6 percent and giving Merkel the combined votes needed to form a viable government.

But following a failure to push through promised tax cuts and a brief flirtation with a more eurosceptic line, supporters left in droves and the party suffered a series of catastrophic regional election defeats.

In recent polls, the FDP has consistently failed to score the five percent required to win seats in the Bundestag lower house of parliament and would be cast into political oblivion if this performance were repeated in September.

The latest survey, published on Sunday by polling institute Emnid for the Bild am Sonntag weekly, put the FDP at four percent.