Leaders from the Social Democrat Party (SDP) of the previous candidate Moshood Abiola and his rival Bashir Othman Tofa from the National Republican Convention (NRC) are meeting to hammer out a joint counter-attack.
The news came as a former head of state, retired general Muhammadu Buhari, said the programme set up in 1987 for the transition to civilian rule was not going to work. In an interview with The News magazine he accused the current government of lacking credibility and said: 'Nigerians must refuse to accept a hostage leadership.'
Since his removal from office in a bloodless coup in 1985, Gen Buhari has kept a stoic silence on national issues and has even avoided meeting his successor in public.
The situation remained reasonably calm yesterday, although students demonstrated in Ibadan, 80 miles north of Lagos, making a bonfire out of disused tyres on the main roads. A similar demonstration was held late on Saturday near Lagos University, police reported, but security forces kept their distance.
The Campaign for Democracy (CD), an umbrella organisation for human-rights groups in Nigeria, said yesterday that it 'totally and unequivocally' rejected the latest twist in the election process.
Beko Ransome-Kutigm, president of the CD, said: 'We continue to recognise the validity of the June 12 elections and we will be battling to have them respected.'
In an address on national radio and television on Saturday, Gen Babangida said there had been corruption during the campaign and accused Mr Abiola and Mr Tofa of spending 'more than two billion naira' (more than pounds 37m) in electoral expenses. But he assured the nation: 'We are committed to handing over power on 27th August, 1993.'
Dr Ransome-Kuti said: 'When he saw them being corrupt, why didn't he arrest them and prosecute them at the time?'
According to unofficial results Mr Abiola won the election, which was later annulled by the government, in the face of a judicial row.
Gen Babangida said the National Defence and Security Council had decided that by the end of July the two political parties - the centre-left SDP and the centre-right NRC - would set up the necessary process for the emergence of two presidential candidates, under the supervision of a recomposed National Electoral Commission.
But Gen Babangida said the candidates should be at least 50 years old, which would eliminate the 46-year- old Mr Tofa, and they must also have been members of their respective parties for 'at least one year', a stipulation that would exclude Mr Abiola.
In the first reactions to Gen Babangida's plans, Alhaji Lateef Jakande, a leading SDP member, said: 'We had elections on June 12. The people elected Abiola. That's the situation today. He is our elected president and Nigerians should support him.'