Nigeria's Goodluck Jonathan hits back at Obasanjo
Nigeria's President Goodluck Jonathan has accused ex-leader Olusegun Obasanjo of threatening "national security" by whipping up opposition to his rule.
Mr Obasanjo had "set the stage for subversion" after making false claims of assassination plots and "high corruption" in government, he said.
Mr Jonathan was responding for the first time to a letter Mr Obasanjo wrote to him earlier this month.
He had called on the president not to seek re-election in 2015.
The public spat between the two men shows the deep divisions that have engulfed the governing People's Democratic Party (PDP), amid fears that it could lose the election under Mr Jonathan's leadership, correspondents say.
Last week, Mr Jonathan lost his majority in the lower chamber, the House of Representatives, after 37 PDP MPs defected to the opposition All Progressives Congress (APC) party.
A powerful faction of state governors have also crossed over to the APC, leaving the PDP with fewer governors than the opposition.
In a rebuttal letter to Mr Obasanjo, Mr Jonathan said his government had taken effective steps to tackle the myriad problems that it inherited when it took office in 2010 - including corruption, oil theft, kidnappings, armed robberies and an Islamist-led insurgency.
"It is very regrettable that in your letter, you seem to place sole responsibility for the ongoing intrigues and tensions in the PDP at my doorstep, and going on from that position, you direct all your appeals for a resolution at me," Mr Jonathan said.
The president said Mr Obasanjo had accused him of putting more than 1,000 Nigerians on a "political watch list, and that I am training snipers and other militia to assassinate people".
Such allegations were "unconscionable and untrue" but he had asked the security agencies and National Human Rights Commission to investigate them, he said.
"Baba [father], I don't know where you got that from but you do me grave injustice in not only lending credence to such baseless rumours, but also publicising it," Mr Jonathan added.
The president said Mr Obasanjo had "surreptitiously" obtained a letter written by Central Bank governor Lamido Sanusi, alleging that nearly $50bn (£30bn) was "unaccounted for" by the Nigerian National Petroleum Corporation (NNPC).
However, the allegation was "spurious" and Mr Obasanjo should apologise for impugning the integrity of the government, he added.
"In closing, let me state that you have done me grave injustice with your public letter in which you wrongfully accused me of deceit, deception, dishonesty, incompetence, clannishness, divisiveness and insincerity, amongst other ills," he said.
Mr Jonathan moved from the vice-presidency to the presidency in 2010 after his predecessor, Umaru Yar'Adua, died in office.
He won presidential elections the following year, with the backing of Mr Obasanjo.
A former military ruler, Mr Obasanjo won democratic elections in 1999 and 2003 on the platform of the PDP.
He stepped down in 2007, after failing to win support to change the constitution so that he could run for a third term.