The ruling African National Congress, or ANC, is virtually guaranteed to win next year's election with party leader Jacob Zuma gaining another term in office -- but the ANC has alienated and angered at least one very important segment of the country's institutions.

As 94-year-old anti-apartheid icon Nelson Mandela lays gravely ill in a hospital, South African churches have vilified the ANC, charging that the party has been subsumed by corruption and moral decay and has also betrayed Mandela's dream of creating a nonracial democracy.

In a vitriolic letter addressed to Zuma, the South African Council of Churches, or SACC, an ecumenical body comprising 26 member churches that played an important role against white minority rule, wrote: "During apartheid, some church leaders wrote to political leaders, but they often failed to listen to these voices. Unfortunately, we find a similar trend today, but it is our duty to speak to you even when we think you might not be listening.

At this moment, we believe that our democracy can be significantly improved. We have begun to stray from the path of building a united, nonracial, nonsexist and democratic South Africa."

The letter was released one week ahead of a crucial ANC party conference, likely to maximize its impact and embarrass Zuma.

The country's leaders, the church group blasted, have "largely lost their moral compass.”

The church leaders also warned that if the government did not address its concerns, it would seek to mobilize society in order to bring about democratic changes.

If political leaders do not take seriously what we are saying, we will continue to strengthen and support the church’s role within the civil society movements, especially those working among the poorest of our people to bring about a more healthy democracy,” the letter declared.

Copies of the letter were also sent to economic chiefs and to Helen Zille, the leader of the opposition Democratic Alliance party.

Criticism of Zuma, who is virtually assured of remaining in power through 2019, has been simmering for years.

Former SACC leader Desmond Tutu has been critical of the ANC's policies and failure to relieve poverty in a country where 25 percent of the population is jobless.

Reuters reported that Zuma's office has received the SACC's letter but would not comment on it.

However, ANC Secretary General Gwede Mantashe criticized the letter, citing that church officials were seeking to sway party policy.

"It is a question of principle," he told South African media. "The ANC must be allowed to run its business."

Zuma himself carries an extraordinary amount of baggage of questionable behavior and conduct, including accusations of rape, as well as using public funds to finance a lavish lifestyle.

In late summer, Zuma's administration encountered its biggest crisis yet, the murder of 34 striking miners by police forces at the Marikana platinum, in a massacre that incited bad memories of the state-sponsored violence of the white-minority apartheid regime.

Moreover, in a country where 80 percent of the population is Christian, the SACC is highly respected.

"This is the very same people who led the church's struggle against apartheid, and it's very significant," Cape Town-based political analyst Nic Borain told Reuters.

"The church clearly believes there to be a significant crisis of both governance and leadership."

Looking at the future of South Africa, the SACC stated, “[The people] yearn for a change from an increasingly corrupt political, business and societal culture to one that is accountable to the people. ... We know that even though the dream of a just, nonracial and prospering democracy is temporarily in eclipse ... the people of South Africa are capable of rising to reclaim their future.”