Nigeria's anti-graft agency has released the names of 135 politicians it alleges are too corrupt to run in the country's elections in April.
Mr Abubakar denies corruption saying he was a lucky investor
Most prominent is Vice-President Atiku Abubakar who defected from the ruling party to run as an opposition presidential candidate.
The Economic and Financial Crimes Commission (EFCC) sent the list with a covering letter to political parties.
Opposition parties criticised the list, saying it was biased against them.
Almost 30 candidates to be regional governors, including seven serving opposition governors, are on the list of those the EFCC alleges are "unfit to hold public office because of corruption".
There are 82 opposition candidates and 53 from the ruling party among the 135 named.
The EFCC, who have been tasked with enforcing President Olusegun Obasanjo's war on corruption, has no powers to ban anyone from the presidential, parliamentary and state elections.
"The list is purely advisory," EFCC spokesman Osita Nwajah told BBC News, adding that it was left to the parties to decide whether to go ahead and field candidates on the list.
The EFCC has consistently said it would not allow corrupt politicians to rule Nigeria, which is considered one of the world's most corrupt countries by the watchdog Transparency International.
EFCC'S GRAFT LIST
Total: 135 candidates
Ruling PDP: 53 (includes 5 for governor)
AC: 27 (includes 1 presidential candidate; 5 for governor)
ANPP: 39 (includes 9 for governor)
Others: 19 (1 for governor, 12 MPs)
An EFCC spokesman said they would prosecute politicians "when the time is ripe", but says the investigation took "several months" and is ongoing.
A spokesman for Mr Abubakar, who has consistently denied corruption allegations, has dismissed the list as a "piece of cheap blackmail".
"We are studying the list and we are considering a legal option because we are sick and tired of these same baseless and careless charges that they keep bandying about," says spokesman Garba Shehu.
A founding member of Nigeria's ruling People's Democratic Party (PDP), Mr Abubakar, was forced out of the party after a bitter feud with President Obasanjo.
He is now running for the Action Congress (AC) party, but has been bogged down in court battles.
"We're not surprised to see that they're going for top opposition figures but only inconsequential people in the ruling party," the AC said in a statement.
"It means nothing in law, it is in bad faith, illegal and a reckless abuse of power."
The main opposition presidential candidate, Gen Muhammadu Buhari, who is generally considered an honest politician by many Nigerians, was not on the list.
Leaders from his party, the All Nigeria People's Party (ANPP) are meeting in the capital, Abuja, and say the EFCC list is top of the agenda.
The anti-graft agency has denied accusations that it targets opponents of Mr Obasanjo, who steps down in April after two terms in office.
The BBC's Alex Last in Lagos says that given Mr Abubakar's legal wrangles it is unlikely that this list will change much.
However, its real impact will be for candidates at the lower level who are still fiercely fighting other politicians for their party's nominations, he said.