Former European Parliament vice-president Eva Kaili must remain in detention on corruption charges, judges in Brussels have ruled.
Kaili is suspected of being at the centre of one of the EU's biggest corruption scandals and her lawyers had requested her release from prison with an electronic tracking device.
Her legal team has now 24 hours to appeal this decision.
Kaili has been in custody since December 9 while her partner, Francesco Giorgi is also jailed.
The two are suspected of working together along with others to funnel bribes from Qatar and Morocco to parliamentarians in exchange for influence on EU policy.
TV presenter-turned-politician Kaili, 44, was removed from her post at the European Parliament last week after charges were laid against her.
The EU assembly has halted work on files involving Qatar as it investigates what impact the cash-and-gifts-for-influence bribery scandal might have had.
Qatar has strongly denied these allegations while Morocco has yet to respond.
The scandal came to public attention earlier this month after police launched more than 20 raids across Belgium and Italy.
Hundreds of thousands of euros were found at a residential home and in a suitcase at a hotel in Brussels.