( L - R ) Obasanjo and Abubakar

LAGOS (Reuters):

The Nigerian opposition party Action Congress (AC) chose Vice-President Atiku Abubakar as its presidential candidate in elections next year, provoking fears of a constitutional crisis.

Abubakar's defection from the ruling party to the newly-created AC followed growing hostility between him and President Olusegun Obasanjo, with each accusing the other of looting public funds.

"We are in grave danger of surrendering our country to a cabal of opportunistic, greedy and hypocritical people which hides under the guise of high moral principles to debase our democratic institutions," said Abubakar after a primary where the 60-year-old former customs officer was the only candidate.

Obasanjo must step down after elections in April which should mark the first handover of power from one elected president to another since independence from Britain in 1960.

Ruling party insiders said Abubakar's new party affiliation could prompt Obasanjo to replace him in a legally questionable move that would significantly raise the political temperature in Africa's most populous country and its top oil producer.

Abubakar has not formally left the ruling People's Democratic Party (PDP), but his allies have set up a factional headquarters and issued statements using PDP letterheads.

"The president could declare the vice-president's position vacant, but that would be another sign of lawlessness," said a senior PDP member, adding that due process required that Obasanjo seek a court ruling before taking any action.

"The president has the use of the police, so he could give Atiku seven days to leave and he could implement it," he added.

END OF DICTATORSHIP

Abubakar's spokesman Garba Shehu said such a declaration would be unconstitutional.

"If some people want to act outside the law, that would be a coup d'etat. It means someone has overthrown the constitution.

"We don't have police or army so we can't fight back but we will go to the courts," he said.

Obasanjo's election in 1999 marked the end of three decades of almost continuous army dictatorship, but politics are still characterised by bribery, violence and rigging.

A U.S.-based political analyst said the confusion caused by any questionable removal of Abubakar could encourage the military to return.

"Unless cooler heads prevail, the country's political system could careen into a constitutional crisis with two vice-presidents by week's end and maybe tempt the military back into politics," said Eurasia Group analyst Sebastian Spio-Garbrah.

Obasanjo's choice to lead the PDP into elections, little-known Katsina State Governor Umaru Yar'Adua, won the ticket at the party's primaries over the weekend.

Critics say Obasanjo chose the reclusive former teacher with a kidney condition because he wants to run the next government by remote control and ensure protection from prosecution in the wake of the sleaze allegations made by his deputy.

The AC last week signed an alliance with the main opposition All Nigeria People's Party (ANPP) under which the two parties agreed to field a single presidential candidate for the elections.

Former military ruler Muhammadu Buhari won the ANPP ticket on Monday, and now the parties will have to choose between two heavyweights of Nigerian politics.

Buhari, whose 1984-1985 rule was famous for draconian austerity measures, is wildly popular among the masses in northern Nigeria but he has limited funds.