Shortly after May returned to Britain from a visit to Turkey, her office tried to calm the waters by saying Britain will "make representations" to the USA government if the ban hits British citizens.
On Sunday afternoon United Kingdom time, as Washington DC woke up, it emerged prime minister Theresa May had asked foreign secretary Boris Johnson and home secretary Amber Rudd to speak to their counterparts in the U.S. to better understand the travel ban.
The Foreign Secretary is speaking to the president's senior adviser Jared Kushner and chief strategist Stephen Bannon to find a way to stop travelling Britons being affected.
London mayor Sadiq Khan lent his voice to calls demanding the US President's state visit is cancelled, with more than 600,000 people signing a petition calling for him to be banned from the UK.
May has been criticized in Britain for refusing to speak out after the president temporarily banned most citizens from Iran, Iraq, Libya, Syria, Yemen, Sudan and Somalia from entering the U.S.as a precaution against terrorism.
But it is unclear if the move by ministers will be enough to quell anger over the ban, much of which was targeted at its discriminatory nature rather than the effect on Britons alone.
Mr Johnson earlier said Mr Trump's ban was "divisive and wrong", and criticised the decision to "stigmatise" people based on their nationality. "Divisive and wrong to stigmatise because of nationality", Johnson wrote on Twitter.
Communities Secretary Sajid Javid also tweeted to say that the United States immigration ban was "not British values".
The Independent understands that shadow foreign secretary Emily Thornberry will table an urgent question on Monday morning, although it must first be accepted by the Speaker of the House.
Theresa May's failure to do that at a press conference in Turkey yesterday led to a backlash from MPs on all sides who had wanted to see a tougher stance - given she had promised not to be afraid to tell Donald Trump when she didn't agree with him.
SNP leader Nicola Sturgeon also voiced her opposition to the state visit, while Labour leader Jeremy Corbyn suggested it should be postponed.
Another of Ms May's Tory MPs, Iraqi-born Nadhim Zahawi, spoke of his sadness that he might now be banned from the States, where his children are studying.
Lib Dem leader Tim Farron said his visit would be "placing the Queen in an impossible position of welcoming a man who is banning British citizens purely on grounds of their faith".
Tory MP Nadhim Zahawi has said he believes the ban applies to him because he was born in Iraq, while four-time Olympic champion Sir Mo Farah, born in Somalia, has said he is anxious he will not be able to travel from Ethiopia, where he is training, to his home of six years in Portland, Oregon.
"Honestly, I don't know what to do and what will happen next, but things are not good", he said.