The former SNP Westminster leader has accused his successor of giving him false information about the party finding a new auditor.
Ian Blackford claims Stephen Flynn phoned him on April 7 to assure him a new auditor was set to be hired.
Flynn has denied those claims.
On Tuesday, Blackford tweeted that he wanted to be “categoric” that Flynn phoned him to make assurances on new auditors.
He said: “Let me be quite categoric that I was phoned on the 7th April by Stephen and told this information.”
Both the SNP and its Westminster group are without auditors after its previous accounting firm quit in September.
Flynn replaced Blackford in December but said he was only told about the issue in February.
If the group fails to submit its accounts by May 31, it faces losing £1.2m in public money which is used to pay its parliamentary staff.
Flynn – the MP for Aberdeen South – previously said he was “hopeful” an auditor could be found soon but said he could not provide “categorical assurances” they would meet next month’s deadline.
He told an Insititute for Government event: “Those that have provided categorical assurances in relation to that would have probably been wise not to have done so.”
Last month, Blackford assured journalists that the party would be able to find auditors in time.
Humza Yousaf – who faces his own July deadline to submit SNP accounts to the Electoral Commission – admitted it would be a “challenge” to meet the deadline.
Approached by STV News, Blackford refused to comment further on the issue.
Flynn has been approached for comment.