She said his failure to intervene “sends a message” that rape victims “will become the accused”.
It comes after a British teenager who had been found guilty of lying about being gang-raped in the Cypriot island of Ayia Napa was on Tuesday sent home after her prison sentence was suspended.
She maintains she was raped and that she faced hours of police questioning with no legal representation. Her lawyers have pledged to overturn the conviction.
Back the UK, the prime minister has faced huge criticism for failing to intervene. The woman has been stuck on the island since 17 July, meaning the case has spanned Mr Johnson’s entire time as prime minister.
The highest ranking government official to speak out about the 19-year-old’s case was foreign secretary Dominic Raab.
Responding to the news of the teenager’s suspended sentence on Tuesday, Ms Nandy, one of six declared Labour leadership candidates, said of Mr Johnson: “The message this case sends to victims is that they will become the accused if they report rape.
“Boris Johnson should have intervened without hesitation.”
It’s the second time in a matter of days Mr Johnson has been accused of failing to address major UK-related issues abroad.
It took him two days to issue a public statement on the US assassination of Iranian general Qasem Soleimani on Friday. Again, Mr Raab had been the highest-ranking government official to comment.
That day, Mr Johnson – who had not received prior warning by the US of the airstrike in Baghdad – was accused by Labour deputy leadership candidate Angela Rayner of being on his “sun lounger” at a time of crisis, adding that “leaving it to the hapless Dominic Raab will not suffice”.
On Tuesday, Mr Raab himself spoke out about the Cyprus rape case, saying he would be following up issues raised with the Cypriot authorities.
“We will be following up on some of the issues in relation to the case. I spoke to the Cypriot foreign minister about that,” he told reporters at RAF Northolt as he prepared to leave for talks in Brussels.
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“There is a broader issue for Brits travelling abroad – not just in Cyprus or indeed in Europe – whether it is holiday, whether it is backpacking, to make sure they can do so as safely and securely as possible.
“What we will want to do is have a conversation with our Cypriot friends and partners about that case once I have downloaded the full facts.”