At least 18 members have quit Cuba’s dissident Ladies in White in the eastern province of Santiago de Cuba. Top opposition leader Jose Daniel Ferrer has been accused of treating a black supporter like a slave. And Ferrer has split from his wife of 20 years.

The two most aggressive opposition movements in eastern Cuba appear to be going through a rough period in recent weeks, forced to deny serious allegations and even hanging up the phone on usually friendly Miami news media.

But dissidents say their troubles are the work of infiltrators from the State Security apparatus in the communist-ruled island, tasked with fueling the jealousies and rivalries that have long riven the opposition, and creating new ones.

“It is very, very clear that all of this comes from people who have a job to do for the political police,” said Ferrer, who served eight years as a political prisoner, was freed in 2011 and is now one of the island’s most respected opposition activists.

The group he founded, the Cuban Patriotic Union (UNPACU), is the most combative dissident faction in Santiago. Earlier this year it forged a national alliance with Guillermo Fariñas, winner of the European Parliament’s $67,000 Sakharov prize.

Authorities meanwhile have repeatedly cracked down on the Santiago branch of the Ladies in White as they push to win the same right to stage public protests as their counterparts in Havana, who march along an avenue after Sunday Mass.

At the root of the split within the Ladies in White is a push by several members to expel a woman repeatedly accused of being a State Security infiltrator and inventing gossip about infidelities by the group’s members or their husbands.

Group leader Berta Soler in Havana acknowledged that she and Santiago leader Belkis Cantillo opposed expelling the woman during a June 18 meeting in Santiago because it would be essentially undemocratic to drive her out without hard evidence.

“We are learning each day how to live with infiltrators. It does not worry us,” Soler told El Nuevo Herald by phone from Havana. “We are not going to waste the time that must be used to continue working for human rights.”

In a statement issued June 30, Soler had declared: “We will not fall into the foolish game of you tell me and I tell you … There are no proofs that she is an agent … so she will continue being a member until it is proven.”

That statement acknowledged that 18 Ladies in White in Santiago had resigned. Ferrer, who is married to Cantillo, said last week that the number of resignations had climbed to 27. Several calls to Cantillo’s cellphone went unanswered.

Ferrer said he separated from Cantillo after 20 years of marriage because of her attitude toward some of the Ladies in White who want to expel the alleged infiltrator. The women who resigned remain members of UNPACU, he said.

State Security agents have repeatedly infiltrated and in some cases founded opposition movements during the five decades of Castro rule, to spy on the groups and exacerbate the many rivalries and tensions that have historically hit the dissident movements.

Soler and Cantillo returned to Cuba in May after a lengthy trip abroad during which they received a hero’s welcome in the United States and Europe and collected more than $65,000 — a fortune by island standards — in prizes and donations.