LONDON -- U.S. President Donald Trump's order barring U.S. entry to people from seven majority Muslim nations is "divisive, discriminatory and wrong," British Foreign Secretary Boris Johnson said Monday. But he rebuffed calls for the government to cancel Trump's planned state visit to the U.K. because of the temporary ban.

Johnson said he had told American officials that it's wrong "to promulgate policies that stigmatize people on the basis of their nationality."

He told lawmakers in the House of Commons that the Trump administration had assured him that "all British passport holders remain welcome to travel to the U.S.," even if they are also citizens of one of the seven countries.

Confusion has reigned about whether dual nationals are affected by the 90-day ban on citizens of Iran, Iraq, Sudan, Somalia, Syria, Yemen and Libya.

Britain's three biggest opposition parties have all called on the government to revoke Trump's state visit, planned for later this year.

Several thousand protesters demonstrated near Prime Minister Theresa May's Downing Street London residence Monday evening, chanting "Donald Trump has got to go" and "Shame on May." Some placards branded the prime minister "Theresa the Appeaser." It was the largest of a series of protests across the country, including in Oxford, Manchester, Newcastle, Cardiff and Glasgow.

"Friends, first they came for the Muslims," Scottish National Party lawmaker Angus Robertson told the London crowd. "But we say something -- and we say no state visit for Donald Trump."

An online petition opposing the trip has more than 1.5 million signatures. Any petition with more than 100,000 signatures must be considered for a debate in Parliament, though not a binding vote.

State visits involve lavish pomp and ceremony, generally with a stay at Buckingham Palace as the guest of Queen Elizabeth II. Some Trump critics say he should not receive the privileged reception.

But May said during a visit to Dublin that she had issued an invitation, "and that invitation stands."

Johnson also said the visit should go ahead.

"He is the elected head of state of our closest and most important ally and there is absolutely no reason why he should not be accorded a state visit, and every reason why he should," Johnson said.

Opposition Labour Party lawmaker Yvette Cooper was one of several legislators to accuse the government of a weak response.

Noting that Trump's order had been signed on International Holocaust Remembrance Day, Cooper told Johnson: "For the sake of history, for heaven's sake have the guts to speak out."

During an emergency House of Commons debate on the ban, former Labour leader Ed Miliband said the travel ban amounted to "perversity, discrimination and divisiveness at its heart" and would make the world a more dangerous place by handing a propaganda coup to Islamic State extremists.

Conservative lawmaker Nadhim Zahawi, who was born in Iraq, urged Trump to "remember the values on which his great country was built" and to rescind the ban.

Another lawmaker from the governing Conservatives, Simon Burns, said: "I suspect that Miss Liberty is holding her head in shame at the moment" because of the order.

Furor over the travel ban has tarnished what British officials had considered a highly successful trip to Washington by May, who met Trump at the White House on Friday -- the first foreign leader to visit the president since his inauguration.

Criticism of May's wooing of Trump erupted when -- only hours after the prime minister had left the White House -- the president signed an executive order imposing a 90-day entry ban for citizens of the seven countries. The order also bars all refugees entering the country for 120 days.

Trump's travel ban sparked protests at airports across the U.S., and drew condemnation and concern from around the world.

The website of the U.S. Embassy in London on Monday advised nationals of the seven countries -- "including dual nationals" -- not to book visa appointments, saying their applications would not be processed.

The advice was removed from the site before Johnson's statement to Parliament.

Jacob Parakilas, assistant head of the U.S. and the Americas program at the Chatham House think-tank , said details of the ban were still unclear. He said there was "a great deal of diplomatic work to be done to soothe tensions with a lot of countries that are allied with the United States."

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Lynne O'Donnell contributed to this story.