FRANKFURT (Reuters) - Tesla accused Germany's IG Metall union of trying to sow unrest at the EV maker's gigafactory near Berlin by seeking to oust the head of the works council, in the latest sign of the sour relationship between the two sides.

IG Metall, Germany's most powerful union, said earlier it had filed a motion with a local court to remove the plant's works council head - who is not a member of the union - from the committee.

The union cited violations to German labour law restricting IG Metall's influence and preventing it from properly representing workers' interests.

The move, which Tesla described as "desperate", reflects IG Metall's efforts to improve what it says are sub-par conditions at the factory, the only car plant in Germany not governed by a collective wage agreement.

The U.S. EV maker is fighting a similar battle in Sweden, where it also refuses to sign a collective wage agreement and is facing multiple lawsuits from the local union.

It is also embroiled in a series of legal disputes in the United States over employment practices, including cases alleging unlawful anti-union conduct.

Tesla denies that its working conditions are below average, saying it offers equal or better terms than those negotiated by unions.

"Since the start of the Gigafactory Berlin-Brandenburg, IG Metall has repeatedly tried to cause unrest in our factory and put obstacles in the way of our success strategy," Tesla said in a statement.

"Our independence and the resulting good working conditions and secure jobs at our plant are a constant source of annoyance for the union."

Earlier this year, IG Metall failed to gain a majority in the Gruenheide gigafactory's works council, winning 40% of seats in what it says is a pro-management group.

In October, the union accused the plant's management of "aggressive tactics" against workers trying to unionise after it fired a union representative from the council.