When Marietje Schaake was elected to the European parliament for the Dutch liberal D66 party a decade ago, she knew what she wanted to do – protect people’s rights online and promote transatlantic relations.

Schaake had not bargained for comments on her clothes and weight, or unwanted advances from male colleagues. As she left parliament after 10 years as an MEP this month, she wondered if her younger self would have been “courageous enough” to run for office had she understood “what I was getting myself into”.

Having published her 2009 election manifesto as a series of tweets, the tech expert was 30 when she first walked into the European parliament buildings. “I was automatically assumed to be an intern or an assistant,” Schaake said. At a reception, a man plucked her drink out of her hand, assuming she was a waitress.

Schaake does not blame people who mistook her for an assistant, since so few people her age were MEPs, but said she has no time for the “culture of sexism, underestimating women [and] unpleasant behaviour” she says she encountered in the European parliament.

A record 40% of MEPs are women, up from 30% when Schaake entered parliament. But while more than half of Sweden’s European representatives are women (55%), Cyprus does not have a single female MEP and Slovakia only has two out of 13. The UK is on 47%, similar to France, Spain, Austria and the Netherlands. Across the 28 countries represented in the parliament, attitudes to women in politics can vary as much as the weather or food.

“The whole idea that a woman my age would be a politician was deemed to be exceptional,” she said. People often asked what her father did. “I later understood [the question] was implying that maybe he was a donor to the party, that I had come from a political family,” Schaake said, the hidden assumption being that her career would not have taken off without patronage.

There was the blunt observation she had lost weight, “inappropriate gifts” such as poetry and champagne, or late-night text invitations to continue negotiations in a hotel room. Once, a male colleague asked her why she was wearing flat shoes. “Why are you?” Schaake replied. On other occasions, she was lost for words. “You don’t have a good answer right away, and later on you kind of hate yourself for not pushing back harder,” she said.

Soon to take up a job in the US involving technology, Schaake said she never wanted to go public with her experiences. “This is really an issue that most women recognise but it’s also a taboo, because you often feel a bit embarrassed, uncomfortable. It’s hard to be the person who talks about this. Is this a traumatising experience? No? Is this a culture that needs to change? Yes,” she said.

The latest intake of MEPs have been required to sign a declaration of appropriate behaviour. Photograph: Frederick Florin/AFP/Getty Images

Following the #MeToo movement, European parliament workers began to come forward with stories ranging from lewd comments and gestures to sexual assault. A blog, MeTooEP, launched last October in response to frustration that the institution was dragging its feet on action to combat sexual harassment. The Guardian has not independently verified these claims.

Schaake said MEPs’ assistants, often twentysomethings in their first job and grappling with life in an unfamiliar city, are the most vulnerable. “I believe this is about abuse of power and that it needs to be addressed as such,” she said.

The stories echo those from Westminster, which has been urged to adopt new employment practices after staff told an official inquiry they had experienced harassment from MPs.

Schaake was known as an MEP for being an advocate of human rights, free trade and cybersecurity who wanted Europe to have a more powerful role in the world. She was number 17 on the Politico website list of “40 MEPs who matter” – a sign of her profile in the 751-member parliament.

She said the reverential culture towards politicians in some countries had compounded the problem of sexism, with some MEPs treated like “demigods”.

The latest intake of MEPs have been required to sign a declaration of appropriate behaviour, which includes pledges to refrain from discriminatory language and demeaning actions. Last year, the European parliament called for all MEPs and staff to receive mandatory training on sexual harassment.

Schaake said it was “a start to raise awareness and also to manage expectations”, but she would also like to see a stronger system for investigating complaints. Currently, the European parliament president rules on whether harassment has taken place after an investigation by a committee of MEPs.

“Being confronted again with these people is unavoidable. So there needs to be real oversight,” she said.