The Greek MEP at the centre of a scandal over corruption allegations linked to Qatar that have rocked the European Parliament was denied release from pre-trial detention on Thursday, prosecutors said.

Eva Kaili, 44, was one of four suspects arrested in Belgium earlier this month. She has protested her innocence and had asked the custody hearing to grant her release under electronic surveillance -- a request that was denied.

Her lawyer, Andre Risopoulos, told AFP that she would not appeal the decision, meaning that she will remain in custody for at least another month while investigations continue. 

Risopoulos had told reporters before the court's decision that Kaili was "cooperating in an active manner" with the Belgian investigation and was willing to wear an electronic device to track her movements if she were released.

Eva Kaili has been charged with corruption. Photo: AFP

Kaili, a former newsreader booted from her post as parliamentary vice president after police raids this month, has become the public face of the alleged corruption case. 

Qatar officials have insisted the Gulf monarchy played no role in any wrongdoing.

Another of Kaili's lawyers, Michalis Dimitrakopoulos, on Wednesday told reporters she feels miserable, "very troubled" and betrayed by her boyfriend and co-accused Francesco Giorgi.

He argued that Kaili was "not a flight risk and not in a position to destroy evidence".

Eva Kaili and her partner Francesco Giorgi. Photo: AFP

She was arrested on December 9 as Belgian police, searching a number of addresses, found 1.5 million euros ($1.6 million) in cash. 

Closed door hearing

Kaili was charged shortly afterwards and has been in detention since.

Another three suspects -- her partner Giorgi; the head of an NGO allegedly used to funnel money; and a former MEP-turned-lobbyist, all of them Italian -- were also arrested.

All four are charged with "criminal organisation, corruption and money laundering".

A Belgian judge authorised Kaili's arrest and detention on grounds she was allegedly caught red-handed with cash, meaning her usual parliamentary immunity could not be invoked.

Belgian Federal Police shows the money seized at the home of Italian former European Parliament member Pier Antonio Panzeri and at Greek EU parliament vice president Eva Kaili's flat and in her father's hotel room

Separate investigations have begun in Italy and Greece, and on Thursday Greek judicial sources said they had seized a 7,000-square-metre (1.7-acre) plot of land bought by Kaili and Giorgi on Paros, in the Cyclades islands, and frozen a bank account held by the couple.

The MEP denies receiving money from Qatar in exchange for influencing decisions affecting it in the EU parliament.

Qatar also denies the bribery allegations and has warned that continued linkage of it to the scandal could "negatively" impact ties and its natural gas supplies to the European Union.

Kaili's hearing was conducted separately from the three other suspects, who appeared before a Belgian court on December 14.

On that date, the court ordered Kaili's partner Giorgi and the former MEP, Pier Antonio Panzeri, to remain in jail.

Former MEP, Pier Antonio Panzeri, has also been ordered to remain in jail. Photo: AFP

The NGO head, Niccolo Figa-Talamanca, was ordered to wear an electronic bracelet to track his movements, but that was suspended on appeal.

Euros in a suitcase

Kaili's Greek lawyer Dimitrakopoulos said the day before the December 14 hearing that she did not know of the existence of the cash -- 150,000 euros, according to a Belgian law enforcement source -- found in her home.

Risopoulos told Belgian newspaper Le Soir that she strongly denied that she had "partially confessed".

He contradicted reports saying she had admitted to asking her father to remove the money uncovered at her address.

Kaili's father was held in custody for two days after the police searches before being released.

Panzeri's wife and daughter were arrested in Italy under a European warrant and could face extradition to Belgium in January to answer charges.

Apart from the money found in Kaili's Belgian apartment, police discovered 750,000 euros in a suitcase with the father, and another 600,000 at Panzeri's place.

An international union leader, Luca Visentini, said on Tuesday he had received 50,000 euros from Panzeri's Fight Impunity NGO.

He said the cash was to cover expenditure for his campaign to take over as general secretary of the International Trade Union Confederation.

Visentini, who was detained for questioning but released while remaining a suspect, was suspended by the union's board on Wednesday pending internal investigations.