Maria Fernandez said she felt "betrayed" after the 'Sunday Mirror' claimed in a report that the 59-year-old Vaz paid for two male prostitutes and made references to drugs, but has decided to give him a second chance.
"The shock was also the whole scenario of allegedly using sex workers because it is so unlike him," the 'Sun on Sunday' quoted her as saying.
Her comments came as it emerged that local police in the influential Labour MP's Leicester constituency had been looking into claims of misconduct.
According to a 'Sunday Times' report, four witnesses, including a former lord mayor of Leicester, last week confirmed they had been interviewed by Leicestershire detectives.
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The inquiries have been going on for at least a year.
Leicestershire police refused to comment last week on whether Vaz was under investigation or whether the witnesses were being interviewed as part of a wider inquiry.
The witness said he was concerned about whether the intervention was an abuse of public office.
Andrew Bridgen, the Conservative MP for North West Leicestershire, said he had been aware of inquiries by Leicestershire police involving Vaz since last summer.
He said John Bercow, the Speaker of the House of Commons, had declined to raise the matter with the force.
He said that to a casual observer the affair had "all the hallmarks of an establishment cover-up".
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Meanwhile, Scotland Yard had confirmed on Friday it was considering whether Vaz had committed any offences in his involvement with male prostitutes revealed last weekend.
Vaz is not under any formal investigation yet and he has not issued a comment on the latest claims.
The high-profile politician is also alleged to have told the escorts to bring the party drug known as "poppers" and is also quoted as discussing the possibility of paying for cocaine at a future meeting, but added that he would not take the drug himself.
Vaz, a Leicester East MP for Labour since 1987, was born to Goan parents in Aden, Yemen, in 1956 and went on to study law at Cambridge University. He served as minister for Europe in former prime minister Tony Blair's cabinet, becoming the first Indian-origin minister to occupy a senior cabinet portfolio at the time.