Abuja - President Muhammadu Buhari may not name a cabinet until September as he takes time to find credible ministers and build a government untainted by the corruption of the past, a senior official and party sources said.
Buhari swept to power in March on an anti-graft ticket and was sworn in on May 29 but critics are starting to ask why ministers for Africa's biggest economy have yet to be unveiled a month after he came into power.
His defeat of incumbent Goodluck Jonathan was seen as a positive step for Africa's top oil producer, given the corruption scandals that have blighted previous administrations.
But Nigeria's financial markets are starting to suffer as the post-election euphoria fades and the lack of a cabinet leaves investors waiting in vain for policy direction on issues as important as the currency and petroleum investment.
"It will take the next two months before ministers can come on board. Bringing them in now may disrupt the clean-up going on. So Nigerians just have to be patient," presidential media adviser Garba Shehu told Reuters. "We need to clean up the mess everywhere before the ministers can come."
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Buhari's anti-corruption drive has been at the heart of his moves so far, alongside efforts to establish a military force with Cameroon, Chad and Niger to fight the six-year Boko Haram Islamist insurgency in the northeast.
While Buhari has not named any ministers, he dissolved the board of the Nigerian National Petroleum Company (NNPC) last week and the state oil firm's management may be next to go.
The National Economic Council, a presidential advisory group that met this week for the first time since Buhari was inaugurated, said the NNPC had kept nearly half Nigeria's oil revenues from 2012 to May 2015 and promised an investigation.
Parliament also agreed last week to investigate contracts between the NNPC and oil trading houses, in which crude was swapped for refined fuel products, on the grounds that there was a gap between the value of the oil delivered and fuel received.
"President Buhari's cabinet won't be ready until early September because he is not in a hurry," a senior member of his All Progressives Congress (APC) party said. "He is just being meticulous so that he can bring in credible and competent hands."
However, some APC insiders say a power struggle between Buhari and party leader Bola Tinubu, a former Lagos state governor and one of Nigeria's most formidable political godfathers, lies behind the delays.
The opposition People's Democratic Party (PDP) said it was concerned Buhari had not made key appointments and the first month of his tenure had been "all motion, no movement".
Yvonne Mhango, sub-Saharan Africa economist at Renaissance Capital, said the uncertainty was exacerbating jitters about the outlook for an economy battered by depressed oil prices.
"We hope we'll get clarity on what sort of policies we should expect and investors can make decisions on the back of that," Mhango said.