The Fianna Fail-Progressive Democrats presidential candidate, Prof Mary McAleese, will not publicly identify her supporters within the unionist community.
Prof McAleese has said on numerous occasions in response to questions about her nationalist background that she received messages of support from unionists.
The Irish Times asked her election office on Tuesday to provide the names of six unionists who supported her campaign.
Her spokesman named an Ulster Unionist Party councillor, Lieut Col Harvey Bicker, from Ballynahinch in Co Down. Col Bicker has already publicly backed her in an RTE broadcast.
Over subsequent days the spokesman said it was unreasonable to ask for the names of people who had sent private letters.
Most of the letters had been marked confidential and it would be difficult to contact all those people to get their permission to use their names, he said.
Last night the spokesman denied that Prof McAleese was unable to back up her claim of unionist support. It was impossible to identify people because of the nature of the support, he said.
"She got a letter from an RUC man wishing her the best. He didn't sign his name and he said he's looking forward to a time when he can sign his name."
There had been a large number of letters from "ordinary members of the unionist community who are not highly politicised," he said.
The McAleese office was also asked on Tuesday to give the exact number of letters of support received.
The spokesman said last night there had been a "good number". It had not been possible to count them, as there were two sacks full of letters of support. "There was a healthy representation from the unionist community."
On Thursday Prof McAleese was asked if she would reveal the names of her unionist supporters to satisfy public curiosity. She said: "You could feed people's curiosity for ever and ever."
She had a "large quantity of correspondence, letters and faxes" from these people. When asked to quantify the figure she said that she "honestly hadn't counted them."
In a statement that day Mr Chris McGimpsey, a councillor, said her repeated assertions that she had support in the unionist community in Northern Ireland were misleading and a fiction.
Prof McAleese said she had never suggested that she could represent the unionist community. What she had said was that she was very encouraged by the amount of support she had received from people of "the unionist persuasion".
When she opened her campaign in Dublin last month Prof McAleese was asked about her ability to work with both communities in Northern Ireland.
She had received "literally a mountain of correspondence and phone calls" from unionists, she said.
