The National People's Party (NPP) claims it has unmasked and kicked out hundreds of Central Intelligence Organisation (CIO) agents and Zanu PF spies planted to destabilise the opposition formation.
Led by former Zanu PF and State vice president Joice Mujuru, the party has suffered defections and resignations by top officials, potentially destabilising it ahead of crunch elections next year.
However, officials say those either defecting to other parties or claiming they were resigning had been exposed as government and ruling Zanu PF party agents.
NPP spokesman Gift Nyandoro told NewZimbabwe.com Thursday that the party's "capable" and "vigilant" security department had exposed the spies.
"We have a report which says that CIO had tried to deploy about 500 CIO and Zanu PF members into the structures of NPP and we are happy to inform our members and the public that the plot totally failed," he said.
"Those few who managed to infiltrate us have found the tight security in NPP fishing them out. They were trying to try influence the process of building a coalition with other political parties.
"Some were instructed to take up influential posts and be 2018 candidates only to resign after nomination, the same strategy used against the late Edgar Tekere's Zimbabwe Unity Movement (ZUM)."
Nyandoro said the CIO was fulfilling what President Robert Mugabe said when Mujuru formed her party after being fired from government and Zanu PF.
Mugabe had accused his deputy of plotting to illegally remove him from power.
The former vice president initially formed ZimPF but established NPP after a bitter falling out with allies who had been expelled from Zanu PF with her.
"Zimbabweans, remember Mugabe declaring that there will be ZimPF 1, 2 and 3!," said Nyandoro.
"After they (CIO agents) failed in their mission, they thought that resignation of individuals would portray NPP as a Zanu PF project.
"NPP, in most cases, has acted silently to remove these individuals who would then rush to newspapers to announce their resignation."
Mujuru's party continues to suffer resignations by senior party members, most of them accusing the former vice president of clandestinely working with Zanu PF.
Nyandoro was however, defiant.
"NPP will never remove the eye from the ball," he said.
"NPP will mobilise, recruit, organise and educate the masses on the importance of registration to vote, and to finally vote out Zanu PF in 2018."