Ms Graessle's proposal was backed by 477 MEPs in Strasbourg
The European Parliament in Strasbourg has backed a call for MEPs to stop employing their husbands and wives.
German MEP Ingeborg Graessle, who proposed the ban, said there was a "very serious conflict of interests".
British MEP Diana Wallis, who employs her husband said she was disappointed but accepted that in some countries there was a strength of feeling.
The vote is not legally binding, but Ms Graessle hopes to have it adopted by the parliament's internal body.
Her amendment was backed by 477 MEPs and opposed by 149. "It was a very clear majority and we should draw conclusions from that," she said.
Although the extent to which family members are employed is unclear, it is a common practice among British MEPs which evolved because of the need to run a political office at home, out of normal office hours.
MEP Gary Titley, who is leader of the British Labour group in the European Parliament, says his wife Charo is a qualified trilingual secretary and her pay is based on Labour party rates.
What is important for him is that MEPs' staff should be qualified and doing a job and that the system is transparent.
"She brings all my paperwork home on a Friday and works from home when I need her working from home. For most people, it's somebody you can trust."
Diana Wallis' husband Stewart Arnold has worked for her for the past seven years.
"He does a good job. We have always worked together. Politics is our baby," she said. "He will have to re-think his career. I could say, after today, I really wonder whether my future lies here."
What disappoints her about the vote is that the parliament usually respects what she see as cultural differences.
But the idea of paying a family member a salary is anathema to German politicians and is generally avoided by MEPs from Nordic countries and the new member states.
"The Germans never did it, the Austrians never did it. We see the public and the press are very clear about this," says Ms Graessle, who believes that the issue could encourage the idea that public funds are misused by EU politicians.
"I don't want to be criminalised. I'm a hardworking member," she said.
Mr Titley accepts there are different political traditions and argues that if MEPs are banned from employing family members, then they should go further.
"If this is the price for maximum transparency, then it's a price worth paying for a package which sorts out all the problems," he says.
A working group is currently considering the rules for MEPs and their assistants.
A final decision will have to be taken by the parliament's internal political body, known as the bureau, which is made up of the president, vice-president and MEPs known as quaestors who are responsible for financial matters.