World Bulletin / News Desk
Alex Rowley, a member of the devolved Scottish Parliament, faced claims carried in local media of harassment and abusive behavior towards a former partner.
In a statement, Rowley said: "I totally refute these allegations and will take all steps necessary to clear my name."
Rowley took over leadership of the party in August this year after former leader Kezia Dugdale reigned.
The resignation is the latest in a string of claims and accusations of misconduct to have engulfed Britain's political class.
Another Labour lawmaker, who had been suspended while he faced an inquiry into allegations about his personal conduct, was found dead at his home last week.
Labour's Carl Sargeant, 49, had been a minister in Wales's devolved government.
The slew of allegations -- which range from inappropriate behavior to rape -- have even reached into Downing Street, the heart of the executive.
On Monday, a female television writer claimed a member of former Prime Minister David Cameron's team had groped her during a visit to Number 10.