Germany's conservative leader tells voters to avoid the liberal FDP

German opposition leader Friedrich Merz took aim at the pro-business Free Democrats (FDP) on Thursday, saying that any votes for the party could end up being a waste and to cast ballots for others.

The FDP has long been viewed as a traditional partner of Merz's centre-right Christian Democrats (CDU), but have been mired in poor approval ratings and in polls are hovering below the 5% threshold usually needed to take seats in German parliament.

"Four percent is 4% percent too much for the FDP and 4% too little for the CDU/CSU," Merz told the Funke Mediengruppe newspaper chain and the French newspaper Ouest-France, referring as well to the CDU's Bavarian sister party, the Christian Social Union (CSU).

"Voters need to consider whether votes for the FDP are ultimately lost votes," he said.

The FDP's leader, ex-finance minister Christian Lindner, has actively appealed to CDU/CSU voters for support and urged Merz to commit to a possible coalition after the February 23 election.

Lindner's liberal party has struggled in the polls since the messy collapse of their three-party coalition with Chancellor Olaf Scholz's centre-left Social Democrats (SPD) and the Greens.

Merz has faced intense controversy for forcing a vote last Friday on a divisive slate of hard-line migration policies, which would have relied on votes from far-right Alternative for Germany (AfD) lawmakers to pass.

But the vote fell short, in part because the FDP faction in parliament split over the issue, as well as because members of Merz's own conservative CDU/CSU bloc skipped the vote.

Merz criticized the division within the FDP on the proposal: "This is likely to have an impact on the elections."