(CNN) — North Carolina and Mississippi's controversial new laws affecting LGBT rights are already threatening to cost the U.S. states millions in lost business and tourism.

That situation could be set to worsen after the UK government updated foreign travel advice warning British citizens about risks visiting America's south.

The update issued by the UK Foreign Office on its website under the heading of "local laws and customs," highlights potential problems for lesbian, gay, bisexual and transgender (LBGT) people.

"The U.S. is an extremely diverse society and attitudes towards LGBT people differ hugely across the country," it says. "LGBT travelers may be affected by legislation passed recently in the states of North Carolina and Mississippi."

The warning comes just ahead of President Obama and Michelle Obama's visit to the UK to celebrate Queen Elizabeth's 90th birthday.

The U.S. is now one of a number of countries and territories about which the UK Foreign Office offers advice to LGBT travelers.

In its general advice, it states that attitudes around the world "can be very different to those of the UK," but travelers are unlikely to have any problems if they prepare well and research their destination before they go.

North Carolina's "bathroom law"

The North Carolina "bathroom" law, also known as HB2, put in place a statewide policy banning individuals from using public bathrooms that don't correspond to their biological sex at birth.

It also stopped cities from passing anti-discrimination ordinances to protect gay and transgender people.

The law has faced staunch opposition from gay rights groups since it was passed in March and provoked a wider backlash.

Celebrities including Bruce Springsteen, Ringo Starr and Pearl Jam have canceled concerts in North Carolina.

The city of Raleigh has already lost around $3 million in lost tourism and business cancellations, according to the Greater Raleigh Convention and Visitors Bureau.

Dennis Edwards, the bureau's president and CEO, told the Guardian last week that another 16 bookings worth $44 million are at risk.

Mississippi's House Bill 1523

Mississippi's so-called "religious liberties" law , House Bill 1523, will take effect in July.

The wide-sweeping legislation would, among other things, allow businesses and religious groups to deny the LGBT community certain services such as counseling, wedding planning and adoption support.

It would protect those groups from punishment if they act "consistent with a sincerely held religious belief or moral conviction."

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The legislation also blocks cities from allowing transgender people to use public bathrooms for the sex they identify as, as well as more widely restricting cities from passing nondiscrimination laws.

Ty Cobb, director of Human Rights Campaign Global, said that the move by the UK government was a "frightening and embarrassing" development.

"It is now more clear than ever that these terrible measures are not only harming individuals and taking an economic toll on the states, but are also causing serious damage to nation's reputation, and the perceived safety of LGBT people who travel here," he said in a statement

More bills pending

Although North Carolina and Mississippi are getting attention, the Huffington Post reports there are more than 100 active bills pending that could affect LGBT people, in 22 states.

U.S. comedy site Funny or Die has lampooned the legislation's potentially dire effect on tourism in a series of parody videos, targeting Mississippi, North Carolina, Indiana and Tennessee.