(Bloomberg) -- Ghana's largest opposition group will hold a protest on Wednesday against the worst blackouts in a decade, hoping to galvanize Ghanaians' frustration and heap pressure on the ruling party.

The economy is already reeling. Factories are slowing output, homeowners are tossing spoiled food from fridges and retailers are spending more cash to buy diesel for generators. The lack of reliable power supply has curbed investor confidence and the government has cut its growth forecast for this year to 3.9 percent, the lowest since 1994, from an estimated 4.2 percent in 2014.

"There's a lack of sympathy for the government as the power outages are widely seen as the result of poor governance," Kissy Agyeman-Togobo, an Accra-based analyst with Songhai Advisory LLP, said in an interview on Feb. 3. "Average Ghanaians feel that they've been failed by the system."

The Electricity Company of Ghana is cutting power to neighborhoods in the capital for 24 hours and then restoring it for 12 hours until the first week of March. Ghana's largest power producer, Volta River Authority, doesn't have enough natural gas to fuel its plants and the water level at the nation's largest hydropower facility is near the minimum necessary to function.

Discontent with President John Dramani Mahama's National Democratic Congress may help to bolster support for the opposition New Patriotic Party ahead of the 2016 ballot, Agyeman-Togobo said.

'Mismanagement' Problem

Slower economic growth and a lack of electricity are not acceptable, Nana Akufo-Addo, the presidential candidate for the NPP, said in an interview on Tuesday. He will lead a march that starts at the traffic circle named after Kwame Nkrumah, who became the nation's first president in 1957 when Ghana won independence from the U.K.

"There's no reason for us to be in this state," Akufo-Addo said. "A lot of it is mismanagement and corruption."

Communications Minister Omane Boamah didn't answer three calls to his mobile phone or return a text message for comment. Power Minister Kwabena Donkor has promised to step down if the situation isn't fixed by January.

The power cuts are known as "dumsor," which means off-on in the local Twi language. Ghanaians have written songs lamenting the outages and new jokes circulate daily on social media. Mahama last month told Ghanaians living in Germany he has been nicknamed Mr. Dumsor.

The state power distributor has curbed electricity to factories, including some operated by Coca-Cola Co. and Unilever NV, for as long as two days at a time starting in December. The Chamber of Mines warned that production at gold mines may fall and that some producers are considering selling mines because of the lack of reliable power. Ghana is Africa's largest producer of gold after South Africa.

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