Opposition candidates seeking to unseat Nigeria’s President Muhammadu Buhari are attacking his economic record and treatment of foreign investors as election season intensifies in Africa’s most populous country. Four members of Mr Buhari’s own party who have defected to the opposition to challenge him are pitching themselves as more business-minded candidates who can jump-start a sluggish economic recovery. Their criticisms in Africa’s biggest oil-producing nation, which is set to hold elections in February, come as two clashes highlight Mr Buhari’s vulnerability on economic policy, even as rising crude prices deliver a boost.

The administration has come under fire for a decision by the central bank and attorney-general to impose $10bn in penalties on South African mobile giant MTN. The president’s office has also lashed out at HSBC over a research note for clients suggesting that Mr Buhari’s re-election would stunt economic growth. His former allies are pouncing on discontent with the economy. The campaign slogan of Bukola Saraki, president of the Nigerian senate, is “Let’s Grow Nigeria”. Aminu Tambuwal, governor of Sokoto state and a presidential hopeful, said “the economy is not showing any real signs of improvement”.

Senator Rabiu Kwankwaso, another contender, said earlier this month that the Buhari administration had “destroyed” the economy. Mr Buhari was considered all but unbeatable as recently as a few months ago. But this week an important state election offered him a stark warning. His All Progressives Congress party found itself in a runoff to defend the governorship in Osun state, which it controls and will be central to the president’s re-election prospects.