Durban - The ANC-NFP coalition signalled a "dark day for democracy in KwaZulu-Natal," the IFP said on Monday.
"This coalition agreement between the ANC and the NFP will only... further decimate the political opposition in KwaZulu-Natal," spokesperson Musa Zondi said in a statement.
Inkatha Freedom Party leader Mangosuthu Buthelezi was "unsurprised" the breakaway party had resolved to work with the African National Congress in all hung municipalities the province.
"I repeatedly warned the electorate that a vote for the NFP is a vote for the ANC. Today my warning has been confirmed."
ANC provincial chairperson Dr Zweli Mkhize said on Monday his party and the National Freedom Party had agreed on a governing partnership in several municipalities in the province.
The May 18 local government elections resulted in 19 hung municipalities in KwaZulu-Natal. The ANC had a majority in 14 of them, the IFP in four and the National Freedom Party (NFP) one - in Nongoma.
If the ANC-NFP pact worked, the IFP would be left in control of only Ulundi and Umsinga. The IFP had the highest number of municipalities in KwaZulu-Natal after the 2006 local government elections.
The agreement announced on Monday was concluded after days of negotiations between the two parties.
Said Zondi: "Thousands and thousands of voters who called for IFP-led municipalities will now have local governments who do not have their best interests at heart."
The IFP had approached the NFP to form coalitions, but the latter said it would not start coalition talks with the IFP until it publicly apologised for comments made before the elections. The IFP had accused the NFP of being an ANC project aimed at destabilising the IFP.
On Monday the IFP repeated these claims, saying the splinter group was being bankrolled by the ANC. Zondi called the NFP the ANC's "clone".
"The coalition agreement proves what we in the IFP have claimed all along, that the NFP is an ANC project and that by joining forces with the ANC in a coalition the NFP is merely coming home."
Mkhize said the ANC-NFP relationship was not based on "political whims".
"It has been founded on the understanding that the communities under the municipalities that will be co-governed by the ANC and the NFP have instructed us to work together to speed up service delivery."
Both the ANC and IFP would retain their independent identity, ethos, policies and right to publicly articulate their views.
Buthelezi said the IFP had "no intention of bowing out" and predicted the NFP would, in time, be "swallowed up" by the ANC.
"We will... champion principled leadership, for the sake of this province, this country and the future."
Zanele Magwaza-Msibi, the IFP's former national chairperson, announced the formation of the NFP, which she had been elected to lead, in January this year.
The relationship between her and IFP leaders began to sour last year when her supporters started campaigning for her to replace Buthelezi as IFP president.