JOHANNESBURG, South Africa – South African President Cyril Ramaphosa described as “treasonous” a campaign ad by an opposition party that depicts a burning national flag, as antagonism between political parties rose three weeks before an election.

The campaign ad released on Monday by the Democratic Alliance uses the burning flag as a metaphor for what it says is the grave risk of the ruling African National Congress retaining power in a coalition with left-wing parties.

“I think it is treasonous,” Ramaphosa told reporters during a visit to Limpopo province.

“It is the most despicable political act that anyone can embark upon,” he said, accusing the DA of desecrating a symbol of national unity.

The business-friendly DA won the second largest share of the vote in the last election five years ago.

This year’s May 29 election is hotly contested, with polls suggesting the ANC will lose its majority for the first time since it came to power 30 years ago at the end of apartheid.

This has raised the possibility that the ANC will have to form a coalition.

The ad shows a flag slowly burning as a voice warns of a disastrous alliance between the ANC, the Economic Freedom Fighters (EFF) and those aligned with former President Jacob Zuma.

An intact flag then unrolls from the ashes of the burnt one as the slogan “Unite to rescue South Africa, vote DA” appears.

“We picked the flag as the clearest symbol of the dream we shared 30 years ago, at the dawn of democracy under President Nelson Mandela. The flames show how his vision has been ravaged by 30 years of ANC rule,” wrote Helen Zille, a former DA leader and chairperson of the party’s federal council, in an opinion column.

Speaking on Radio 702, Zille said the blowback was coming from people who would never vote for the DA anyway.

“It creates a choice. Are you part of burning the flag? Are you part of that brigade, or are you part of those of us like the DA who want to restore the flag?” she said.

DA leader John Steenhuisen has called the prospect of a coalition between the ANC and EFF a “doomsday” scenario for South Africa, but not ruled out partnering with the ANC in government.

The ANC, for its part, has said it will win the election and will not need to go into coalition. The latest opinion poll showed its support at just over 40%.