A former leader of the U.K. Independence Party has announced she is leaving the pro-Brexit party.

Diane James said Monday she is leaving UKIP but will remain in the European Parliament as an independent.

She said her relationship with the party had become "increasingly difficult."

James was elected party leader in September after prominent Brexit supporter Nigel Farage stepped down, but she resigned the top post just 18 days later.

Farage has returned as interim leader. He has remained in the spotlight by forming a friendly relationship with U.S. President-elect Donald Trump.

The party is engaged in another leadership contest, with the winner expected to be announced next week.

UKIP played an important role in persuading British voters to choose to leave the European Union in the June referendum.