Alex Rowley was last night suspended by the Labour Party following claims he threatened and harassed an ex- girlfriend.
Mr Rowley stepped down from his role as acting Scottish leader plunging Labour into chaos while allegations made against him by a former partner are investigated by the party.
Labour suspended the Mid Scotland and Fife MSP after party colleagues expressed their concern at the claims.
Mr Rowley was accused by a 49-year-old woman of ruining her life and subjecting her to three years of torment after they began a relationship.
According to a report published in a tabloid newspaper, the anonymous woman was bombarded with abusive texts from the politician who used to be Gordon Brown’s election agent.
She claimed Mr Rowley “destroyed” her life, describing him as a “ruthless bully” who had become “obsessed” by her.
The mother said she was encouraged to speak out after seeing other women describe their harassment ordeals. She described their relationship as being “like emotional blackmail and abuse”. Mr Rowley refutes the allegations.
At the time she called the police, but no further action was taken after officers investigated.
Mr Rowley is the most senior Labour figure to be affected by the claims of harassment sweeping Holyrood and Westminster. His suspension comes after the SNP MSP Mark McDonald quit his position as Children’s Minister in Nicola Sturgeon’s government after admitting inappropriate behaviour towards a woman.
Mr Rowley was appointed interim Scottish Labour leader after Kezia Dugdale’s unexpected decision to step down.
He has been in charge during the leadership race between Anas Sarwar and Richard Leonard.
Yesterday Mr Sarwar, Mr Leonard and Ms Dugdale all called for Mr Rowley to be suspended after the allegations were made public.
Labour front-bencher Jackie Baillie has taken over as interim leader and will remain in that post until Saturday when the results of the leadership contests are announced.
A statement from Labour issued last night said Mr Rowley had been suspended as a member of the Scottish Labour Parliamentary Group, which means he will have the party whip withdrawn at Holyrood.
He will remain suspended while a party investigation is carried out.
Scottish Labour business manager James Kelly said: “It is important that the investigation into these allegations is fair and transparent.”
Ms Dugdale described the claims as “serious and deeply concerning”.