"It may be that pressure and exhaustion build up and come later. In situations, it has been necessary to put emotions aside, but they do accumulate."
However the striking image proved divisive with some commenters saying it "eroded" her credibility, while another asked if she were being "Prime Minister or modelling?"
Others took to social media to proclaim "I'm with Sanna", sharing pictures of themselves in similarly low-cut blazers.
Some social media users pointed out that Russian leader Vladimir Putin has previously posted topless without suffering the same outcry. Former Aussie leader Tony Abbott was also often snapped in his budgie smugglers at the beach.
The centre-left leader is Finland's youngest PM and the world's youngest female leader. Like New Zealand's Prime Minister Jacinda Ardern, she has harnessed social media to build her popularity, though Ms Marin has featured pictures of her baby bump and wedding in August 2020.
Anu Koivunen, a media scholar and Professor of Gender Studies at Tampere University, told yle magazine that Ms Marin is very "media savvy" so would have known what to expect.
"These politicians know very well what kind of discussions they are starting. They are very media savvy and this social media storm [over Marin's outfit] did not come as a surprise," she said.
"Marin's actions are done with full cognisance. The photo caption in the Trendi article reads that Marin is aware that a woman's appearance is always a matter of debate and that is why she, as prime minister, always strives to dress the same."