The Nationalist Party has been asked to submit its accounts and donations list five times since January 2022, the Electoral Commission said in a legal letter.
"On January 18, 2022, April 6, 2022, January 12, 2023, April 10, 2023 and June 14, 2023, (the Commission) wrote to the Nationalist Party asking it to present the documents as required by law," the Commission said.
The Commission was reacting to a judicial protest by two Labour candidates for the European Parliament elections, Marija Sara Vella Gafa and Daniel Attard.
In January, they called on the Commission to take whatever action was required to make the PN conform to the law and to fine it accordingly.
The PN's donation reports and accounts for 2021 and 2022, have remained unpublished.
Asked in January whether the PN had filed its accounts and donation reports, opposition leader Bernard Grech did not give a straight answer.
"On the party's accounts, we will continue doing our duty as everyone should do," he said.
The requirement for political parties to publish accounts and donation reports was introduced in 2016 through the Financing of Political Parties Act.
Political parties must publish the names of individuals and companies that donate more than €7,000. Political parties cannot receive more than €20,000 in donations from individuals or companies.
Political parties must present audited accounts to the regulator (the Electoral Commission) within four months after the end of their financial year. Failing to do so could lead to a fine of €10,000.
They must also present a donation report within 60 days after their reporting period. Failing to do so carries an administrative maximum fine of €20,000.
However, in its letter, the Electoral Commission said its "hands were tied," following a judgement made by the constitutional court in 2019 which declared that the Electoral Commission could not investigate and decide on cases regarding the party funding law.
"Still, the Commission insists that the parties fulfil their obligations".
In a joint statement, MEP candidates Vella Gafa and Attard said Bernard Grech should "take political responsibility" over the PN's failure to publish their accounts.
They also said Grech "lied" about publishing the accounts.
They were referring to Grech's interview with One News journalist, Samuel Lucas, last September.
When asked whether the accounts for 2021 and 2022 have been published, Grech said: "I am confirming that we publish everything and what is not ready will be published at the opportune time".