Former Finance Minister Tendai Biti's party says President Robert Mugabe's rule has been predominantly a period of "darkness" and the veteran leader must back off and stop making unguarded pronouncements over its intended merger with other opposition forces ahead of next year's polls.
This follows Mugabe's dismissive remarks at a party rally in Mutare on Friday that the envisaged grand coalition, however constituted, would not dislodge his party from power.
Mugabe addressed his former deputy Joice Mujuru, now opposition leader, and Biti as "kaMujuru and kaBiti", Shona prefixes which denote people of little significance.
But the People's Democratic Party (PDP) has come out guns blazing, insisting Mugabe's dismal record at the helm placed him far from being a credible counsellor on how to handle opposition mergers.
"President Mugabe is a little big man who cannot lecture us on any subject let alone give advice on how the democratic contingent must remove him from power," PDP spokesperson Jacob Mafume said in a statement.
"The fact of the matter is that Mugabe has over stayed his welcome; he failed dismally to transform his doomed party from a military liberation machine to a proper transformational civilian political party.
"He continues to live in the past; constantly talking about his liberation credentials more than the people who were at the battle front some of whom he denied National recognition like Lookout Masuku who died under house arrest."
Mafume accused Mugabe of keeping the same repressive tactics used on blacks by the country's former colonial masters.
He said Mugabe's most notable contribution to a country he founded 37 years ago was to merely change its National Anthem twice and hoisting the National flag while replacing the Union Jack "and the rest is darkness".
"Under Mugabe's watch," Mafume added, "the highest number of human rights violations were witnessed; these include loss of lives during Gukurahundi and elections related state sponsored violent episodes especially the 2008 run-off.
"Children were butchered and mutilated while pregnant women were annihilated in cold blood all for the sake of power retention and shocking ethnic hate."
PDP says Mugabe has presided over successive episodes of economic decay which have been worsened by his choice of Patrick Chinamasa as finance minister.
The party further insists the brightest period between the country's economic crises was during the inclusive government era when opposition officials deployed to government corridors helped restore the country onto a brief prosperous path which was later halted by their controversial defeat in the 2013 elections.
"At the present moment Mugabe is presiding over a country with an economy on its knees, a governance crisis which is synonymous to mafia kind of style, a style which reveres corruption as its hallmark," Mafme said.
"He presides over a divided country with so much hatred and hate speech just like Rwanda before the genocide, our local newspapers are reflective of this fact, his criticism of opposition unity is therefore not a surprise.
"He presides over a country with a broken down social contract and moral fabrics in intensive care. It is a country where the citizen hates the site of a police officer."
PDP also scorned the 93 year-old leader for his now common memory lapses as did happen at a rally in Mutare on Friday when he referred to ICTs Minister Supa Mandiwanzira as "President Mandiwanzira".