Letters to a parliamentary assistant, who refused to accept Sinn Fein policy that he should draw only the average minimum wage, reveal how he was berated by the party's head of human resources for not contributing to party funds.
He was repeatedly asked to submit his Oireachtas wage slip to the party's finance section, in order to calculate how much he should pay.
Matt Treacy, a former IRA prisoner, released the demand letters from Sinn Fein last week after the party dismissed his account of being pursued for money as "untrue".
Sinn Fein also claimed that employees' donations to the party are "voluntary" and "by choice". However, the letters to Treacy dispute this claim. Treacy, who was still in the IRA when he started working in Leinster House as an adviser, took voluntary redundancy from his post last year.
In one letter dated 2012, Martin Lynch, Gerry Adams's former driver and now the party's head of human resources, berated Treacy for his "failure to deal satisfactorily" with the issue of the "party wage".
He wrote that the issue was "on-going for years" and "despite many attempts, you have not fully engaged with the process, either to ensure that you are in receipt of the party wage, or to explain in detail why your personal circumstances are such that you might be in need of temporary relief".
He said Treacy's "contribution" had "ranged from briefly accurate, to considerably less than accurate, to none at all". He then invited Treacy to a meeting to "resolve" the situation.
Other letters to Treacy from Sinn Fein's finance manager insist that he surrender his wage slip to the party, saying: "All our paid personnel have to comply with party policy on remuneration.
''In order to ensure that you are within party guidelines, I will be calling in to see you to discuss why you have failed to respond so far. Des Mackin [the party's finance director] will be accompanying me."
The controversial issue of "donations" arose in the context of Sinn Fein's policy of paying all elected representatives and staff the same average industrial wage.
Sinn Fein members on publicly funded salaries - €65,000 to €89,000 for senators and TDs - claim to pay themselves the average industrial wage of €37,000 and divert the surplus to the party.
The letters to Treacy were written between 2008 and 2012. The letters point out that, when Treacy started in Leinster House, his earnings were topped up by Sinn Fein because they were below the average industrial wage. Treacy said the party stopped pursuing him when he sought legal advice from an employment solicitor to say he had a "stateable case" against Sinn Fein. He also called in the trade union, Siptu, for advice.
Treacy claimed Martin Ferris, the TD for whom he worked for most of his time in Leinster House, and who was technically his employer, seemed embarrassed by what was going on.
The ex-IRA man, who has written a book about the last days of the organisation, told the Sunday Independent some people have accused him of "betrayal" for speaking out.
"Others are pleased that someone has spoken out about the internal regime that encompasses a lot of things.
''My being pursued over money is at the moderate end of the scale," he said.
In a statement Sinn Fein said: "As we responded to allegations last week, many Sinn Fein activists make entirely voluntary donations to support the development of the party.
"This is their choice. Mr Treacy did not make any significant donation to the party over the 14 years he was employed at Leinster House. That was his choice."