Foreign minister Martin in challenge to Irish PM Cowen
The Irish foreign minister has tendered his resignation and said he will vote against Prime Minister Brian Cowen in a vote of confidence on Tuesday.
Micheal Martin, seen as a rival for the leadership of the ruling Fianna Fail party, said that the PM had told him his resignation was not necessary.
But he said he believed a new leader was needed before a general election.
Earlier, Mr Cowen said he would stay on as party leader but would offer colleagues a secret confidence ballot.
He has faced recent scrutiny about a meeting with the head of Anglo Irish Bank shortly before he announced a multi-billion euro bank guarantee.
On Thursday, Mr Cowen said he would take 48 hours to consult with his parliamentary colleagues on whether he should continue in his post.
Speaking to assembled reporters in Dublin on Sunday, he said the discussions had been cordial and respectful.
Mark Simpson, BBC News, Dublin
Ireland's economic meltdown has left a political mess. Unity in the main government party, Fianna Fail, has been shattered as preparations begin for the planned general election in March.
Critics of Prime Minister Brian Cowen say a new party leader - not directly associated with Ireland's financial woes - will be required to save Fianna Fail from electoral annihilation.
Friends of Mr Cowen say it is a time for unity and strong leadership. And they say that Foreign Minister Micheal Martin is too weak and indecisive.
By publicly opposing Mr Cowen, it is clear that Mr Martin is determined to prove he is up for a fight. The political mess is about to get even messier.
"As taoiseach (prime minister) my total focus must remain with discharging my duties to the people," he said.
"For Fianna Fail, the party is important but the interests of the country are paramount."
The normal party procedure for removing the leader begins when a quarter of all party MPs sign a notion of no-confidence.
Mr Cowen said he wanted to dispense with those procedures to hold the secret vote of confidence on Tuesday.
On Saturday, one Fianna Fail member of parliament called for the party to unite behind Mr Martin.
Noel O'Flynn said he had been contacted by the prime minister on Saturday afternoon and had told him that his leadership had not worked.
However, deputy prime minister Mary Coughlan has said she believes in Mr Cowen's leadership.
She added: "I believe that he has been the only man over the last two and half years to make the difficult decisions and give the leadership to the cabinet.
"And I would say that if others were in that place, I would question their ability and their acumen to do what had to be done."
Former Anglo Irish chairman Sean FitzPatrick, who Mr Cowen met at a golf course in 2008, is still subject to official scrutiny over his role in the collapse of the bank and has previously been questioned by police.
The prime minister has denied that he discussed bank matters with Mr Fitzpatrick at the golf course and insisted that he had not done political favours for any financial institution.
He is also facing a motion of no confidence, tabled by the opposition Labour Party, in parliament next week.
Mr Cowen, who took power in 2008, has been under pressure since Ireland was forced to seek an international financial bail-out late last year.
Following the intervention by the EU and the IMF, there were rumours of an internal push against him but his critics pulled back at the last moment.
His coalition government has only a slim minority in parliament and a general election is expected in the spring.