The president of the European Parliament will seek Monday to get ahead of a graft scandal that has rocked the legislature, by officially unveiling a series of reforms to clean up the multinational assembly.

But many MEPs and observers believe the changes to be presented by Roberta Metsola don't go far enough to be able to restore credibility in the institution.

The parliament has been the focus of intense scrutiny since the scandal broke open a month ago with the arrest of one of Metsola's 14 vice-presidents after Belgian police raided homes and offices of several MEPs, former MEPs, parliamentary aides and heads of NGOs that dealt with lawmakers.

Belgian prosecutors are investigating alleged graft in the European Parliament benefitting Qatar and Morocco. The police raids turned up 1.5 million euros ($1.6 million) in cash.

Qatar has denied having any role in any wrongdoing in the case. Morocco says it is the target of unjustified "media attacks" over the allegations.

Metsola's arrested vice-president Eva Kaili, a Greek MEP who has since lost that high parliamentary position, also has said through her lawyer that she knew nothing about cash found at her home.

Kaili remains in custody with three other suspects: Kaili's boyfriend Francesco Giorgi, who was a parliamentary aide; former MEP Pier Antonio Panzeri; and Niccolo Figa-Talamanca, head of an NGO suspected of making payments to MEPs.

The three male suspects are all Italian. According to a Belgian media report, Giorgi has made a confession.

All four are charged in Belgium with "criminal organisation, corruption and money laundering". Greece and Italy have launched their own investigations.

Metsola has vowed to act swiftly to "strengthen integrity, independence and accountability" in the parliament. She has also said the graft scandal showed "European democracy is under attack".

On Monday, Metsola will kick off the parliament's first plenary session of 2023 in Strasbourg, eastern France, by formally announcing measures which have already been trailed.

These include restricting parliamentary access for former MEPs; registering outside individuals who lobby, meet or speak at the parliament; a public MEPs' registry of gifts and travel received; and punishment for breaches.

Yet legal experts and some senior MEPs have voiced scepticism that those steps go far enough.

- 'More serious' response needed -

Alberto Alemanno, a professor of EU law at the French business school HEC, said he did not believe that "imposing these few rules would be sufficient to create a new political culture in the European Parliament".

"The scandal is much more serious than others for the credibility of the European Union," he told AFP. "We could have expected a more serious, more structural response than in the past."

Among MEPs, the head of the centrist Renew grouping in the parliament, Stephane Sejourne, said the scandal showed the need to create an EU authority tasked with "transparency in public life at the European level".

Such an idea has been put forward by the European Commission in the past but never got off the ground.

A German Green MEP, Daniel Freund, said MEPs' assets should be publicly listed at the start and end of their mandates, and whistleblower protections should be bolstered.

The co-chair of the EU parliament's Left grouping, Manon Aubry, warned that "it is not acceptable" that more far-reaching reforms MEPs had demanded immediately after the scandal broke had been watered down.

The alleged corruption case continues to roil the legislature.

At the beginning of January, at the request of Belgian prosecutors, the European Parliament started a procedure to lift the immunity of two other MEPs: a Belgian, Marc Tarabella, whose home was among those raided in December; and an Italian, Andrea Cozzolino.

On Sunday, Tarabella acknowledged he had failed to declare a paid-for trip to Qatar in February 2020. His lawyer said it was an oversight.

That came days after another Belgian MEP, Maria Arena, admitted she had "forgotten" to declare a similar expenses-paid trip to Qatar in May 2022.

The scandal threatens to overshadow the parliament's plenary session this week.

After Metsola's presentation of reforms, on Wednesday the chamber will vote on who will succeed Kaili in her vacant parliamentary vice-president's chair.

The danger, observers say, is that the case -- dubbed "Qatargate" by some MEPs and media -- could sully elections for the next European Parliament in 18 months' time.

Public reaction to the scandal is "much stronger -- much more -- than what European leaders want to admit," Alemanno said.