Prime Minister Silvio Berlusconi is refusing to admit defeat in last week's Italian election despite a court ruling in favour of his opponents.
Mr Berlusconi has yet to comment on the court ruling
The Supreme Court has confirmed a narrow win for the centre-left opposition led by Romano Prodi.
But after a meeting with his advisers, Mr Berlusconi let it be known he was considering a further legal challenge.
His economy minister, Giulio Tremonti, told Italian TV that some "anomalies" were yet to be cleared up.
The national co-ordinator of Mr Berlusconi's Forza Italia party, Sandro Bondi, said the court should widen its review to include "irregularities" in overseas voting.
No phone call
On Wednesday, the Supreme Court ruled that Mr Prodi had won the lower house by a margin of some 24,000 votes - a similar margin to the one previously announced.
The court had reviewed 2,100 ballots not immediately included in the overall count, as the voting intentions were not clear.
A review of another 3,100 disputed ballots in the Senate was still under way, but was not expected to affect Mr Prodi's slim Senate victory.
After the ruling, Mr Prodi said there were "no further doubts about our victory".
"We will work to deserve the trust that our voters have shown us and to earn the trust of those who have legitimately decided to vote for the other coalition," the 66-year-old Mr Prodi said.
Asked if he had received a telephone call from Mr Berlusconi, Mr Prodi said: "I'm waiting."
Mr Berlusconi could mount a legal challenge in the days to come but he may find himself increasingly isolated by his coalition partners, analysts say.
However one of the parties in the centre-right coalition, the UDC party, has broken ranks and admitted defeat.
But some analysts believe Mr Berlusconi is simply trying to undermine Mr Prodi's government-in-waiting, hoping it will be short-lived - in effect, conducting the next election campaign.
The court ruling means Mr Prodi can work on forming a government but it cannot be sworn in until parliament picks a new president.
Under the constitution, the president must give the mandate to form a government, and the current head of state, Carlo Azeglio Ciampi, whose term ends in mid-May, has already said he will leave the task to his successor.
The new parliament is scheduled to convene on 28 April.