Polish MEP Ryszard Czarnecki is under investigation by national prosecutors over alleged extortion.
The investigation concerns possible irregularities regarding the reimbursement of travel expenses and payment of his daily allowance.
Czarnecki, a veteran of Poland's ruling Law and Justice party, has been a member of the European Parliament for 16 years.
The former journalist is also listed as a current member of the European Committee on Budgetary Control.
The Polish prosecutor's office is currently dealing with the case.
The European Anti-Fraud Office (OLAF) confirmed to Euronews that they had sent an investigation report, containing judicial recommendations, to Poland in May 2019.
"OLAF also made a recommendation to the European Parliament to recover amounts unduly spent," said a spokesperson.
Polish local media reported that the investigation concerns Czarnecki's expenses when he served as an MEP between 2009 and 2014.
According to the Polish daily Rzeczpospolita, the European Parliament confirmed that it has received final conclusions from OLAF and will take "all necessary steps to recover the money".
From 2014 to 2018, Czarnecki served as a vice president of the Parliament but MEPs voted to remove him from the role after he compared a rival Polish parliament member to a Nazi collaborator.
Parliamentary party leaders had called for Czarnecki’s dismissal over “serious misconduct”.
Euronews has reached out to both Mr Czarnecki and the Polish prosecutor's office for further comment on the investigation but had not received a response at the time of writing.
Former Polish MEP Janusz Wojciechowski was also investigated by OLAF in 2016 over possible abuse of travel and subsistence expenses.
In September, the European Anti-Fraud Office recommended that the European Parliament recover more €11,000 from Mr Wojciechowski and called for administrative rules on MEP reimbursements to be strengthened.
However, no disciplinary or judicial recommendations were made and the sum was paid in full.
In December, OLAF also reported that more than €500,000 of European Parliament funds were misused by members of two pan-European political groups.
Between 2010-2018, OLAF concluded more than 1900 investigations and recommended the recovery of over €6.9 billion to the EU budget.