Prof Mary McAleese last night stood over her claim that she had received a "huge pile" of correspondence from unionists supporting her bid for the Presidency.
But a prominent unionist politician and the editor of the Belfast News Letter both denied that she had strong support in the unionist community.
Prof McAleese said she would not reveal the names of unionists who had written to her offering their support because it would involve breaking confidences.
"I didn't claim ever to have had widespread support, I said that I had received a considerable amount of support across the spectrum of unionism, which I have. I have a huge pile of letters, faxes and e-mails and phone calls from people who have been very, very kind", she said in an interview on the RTE television programme, Prime Time.
She would not produce a list of unionist supporters because the correspondence with her had been in private. "I refuse to open them up as objects of curiosity for journalists, quite frankly. I'd rather take people saying to me that they didn't believe me or whatever . . . I'd rather have that than breach the confidentiality of people who have written to me."
The editor of the News Letter, Mr Geoff Martin, said he spoke to a lot of unionists and he had not met any who would support Ms McAleese in her bid to become President of the Republic. "In fact, the opposite is true, it's almost a case of any candidate but Mary McAleese", he said on BBC television's Spotlight programme.
"She has been anti-British and anti-unionist in some of the sentiments that she has put forward and I think she faces great difficulty if she does become President in embarking on any kind of bridge-building campaign as a result of that", he said.
Mr Peter Weir, a member of the Ulster Unionist Party team at the Stormont talks and a former student of Prof McAleese, said she was widely believed by unionists to have been heavily involved in having the British national anthem and the RUC band dropped from graduation ceremonies at Queen's University.
"I think that Mary McAleese and others who were involved in that decision have to some extent become almost hate figures among certain sections of the unionist community", he said.
Prof McAleese, speaking on the same programme, said that the overwhelming majority of those who had taken that decision on behalf of the senate of Queen's University were drawn from the unionist tradition. She said she was a nationalist but was not antiBritish and celebrated British culture.
Another presidential candidate, Ms Mary Banotti, was criticised on the programme by the editor of the Irish News, Mr Tom Collins. "She's got a partitionist mindset and is not necessarily the type of person who is going to be able to lead a new Ireland into the next century", he said.
Prof McAleese also said last night that she had not spoken of her role in the peace process from the outset of her campaign because it had been a "very modest" one.
"I felt, if I mentioned it at all, they'd have said `gosh, she's claiming ownership of the peace process'," she said. "I felt that my role in this process was so modest and so tiny and so humble that it wasn't worth talking about, quite frankly."
The work she had been involved in with the Redemptorist peace ministry had been "very quiet" and "very silent", she added. "We didn't go around looking for any public trumpeting. I never ever wanted . . . any credit for it in any shape or form. I honestly didn't regard this as something I wanted to promote, not because I wanted to bury it, but because I didn't want people to say `how dare she claim, do you know, that she has credit for the peace process?'."