Theresa May cannot just "show up" to Washington if she wants to be seen as feminist prime minister, the Women's Equality Party (WEP) warned on Monday (23 January).
The group said the Conservative premier must take Donald Trump "to task" when the top politicians meet on Friday.
"If our prime minister really means it when she says she will take Donald Trump to task, then she needs to insist that women in the US and UK have access to abortion and contraception; that survivors of male violence get equal treatment in the justice courts," Sophie Walker, leader of WEP, told IBTimes UK.
"If she means to be a feminist prime minister for women in the UK then she needs to negotiate a trade deal that will result in jobs for women as well as men and economic and social good for the whole country. Faced with a US president who is normalising misogyny, it's not enough to just show up."
The comments come after hundreds of thousands of people protested against Trump in Western capitals, including London, Paris and Washington, on Saturday.
Trump, among other controversies, was forced to apologise in October after a 2005 tape emerged of the property tycoon bragging about grabbing women "by the p***y".
May has described the remarks as "unacceptable", but suggested on Sunday that she would not raise the issue of women's rights with the US president.
"When I sit down, I think the biggest statement that will be made about the role of women is that I will be there as a female prime minister, directly talking to him about the interests we share," she told BBC One's Andrew Marr show.
May will be the third British politician to meet Trump after his election. Former Ukip leader Nigel Farage and Conservative MP Michael Gove, a former Tory leadership rival of May's, have both had audiences with the property tycoon.
Trump, whose mother hailed from Scotland, has indicated that he wants a quick US-UK trade deal.
He has also returned a bust of British war leader Sir Winston Churchill to the Oval Office. The sculpture of the former prime minister was reportedly moved in 2009 to the British Embassy in Washington under Barack Obama.
The bust, designed by Jacob Epstein, was gifted to George W. Bush in 2001.