Members of the European Parliament voted on Thursday to suspend access to the hemicycle's premises to Qatari representatives as the Gulf country is suspected of having offered "large sums of money" and "substantial gifts" to MEPs and assistants in a bid to influence European decision-making.
Lawmakers also decided to halt all pending legislation involving Qatar.
The investigation by Belgian police into undue influence by a Persian Gulf state widely believed to be Qatar has sent shockwaves through Brussels and thrown into question the parliament's transparency and lobbying rules.
Greek MEP Eva Kaili, together with three other suspects, has been charged with participation in a criminal organisation, corruption and money laundering. The four remain in custody.
Kaili has already been ousted from her role as European Parliament Vice President and from her membership in the socialist group, known as S&D.
Police have conducted more than 20 searches since Friday, seized over €1.5 million in cash and frozen IT resources from Parliament employees to prevent the disappearance of key data.
In the resolution passed on Thursday with 541 votes in favour and just two against, MEPs described themselves as "appalled" by the revelations and underlined the "gravity and magnitude" of the case.
The Parliament "denounces, in the strongest terms, Qatar's alleged attempts to influence Members, former Members and staff of the European Parliament through acts of corruption, which constitute serious foreign interference in the EU’s democratic processes," the draft text reads.
"Inappropriate means of influencing, bribery and other criminal offences are unacceptable."
MEPs asked for a suspension of the access badges issued to "representatives of Qatari interests," which might go beyond Qatari nationals, until the investigation further clarifies the facts.
All the EU institutions require identity badges to be entered.
Moreover, lawmakers decided to put on hold "all work on legislative files relating to Qatar," particularly the EU-Qatar aviation agreement, which is yet to be fully ratified, and the controversial visa liberalisation for Qatari and Kuwaiti citizens.
The visa waiver had been approved earlier this month by the parliament's civil liberties committee with 42 votes in favour, including Kaili's, and 16 against, and was expected to be sent to the full plenary.
It's unclear when discussions around the file will resume.
MEPs will also cancel all "planned visits" to the Gulf country, which is currently hosting the FIFA World Cup, and requested an EU-wide ban on political donations made by countries outside the bloc.
"Trust in Parliament's integrity and the rule of law is paramount for the functioning of European democracy," lawmakers said in the motion, sponsored by six political parties.
"It is key to ensure that democratic processes are not captured by private and external interests."
In addition to this, the resolution calls for an in-house investigation, a special committee on transparency and integrity, and a "dedicated" vice-president in charge of fighting corruption and foreign interference.
MEPs also call for stronger rules to protect whistle-blowers, monitor so-called friendship groups and regulate "side jobs," as well as making the EU Transparency Register mandatory.
Similar proposals were unveiled earlier on Thursday by European Parliament President Roberta Metsola, who promised to launch a "wide-ranging" reform process to crack down on corruption and illicit lobbying.
Since the graft scandal erupted over the weekend, the Qatari government has taken a firm stance and distanced itself from Kaili and the other suspects.
"The State of Qatar categorically rejects any attempts to associate it with accusations of misconduct. Any association of the Qatari government with the reported claims is baseless and gravely misinformed," the Qatari Mission to the European Union said in a statement.
"The State of Qatar works through institution-to-institution engagement and operates in full compliance with international laws and regulations."