LGBT and civil rights groups are mobilising for a nationwide battle to safeguard the gains of the marriage equality movement, in the face of a gathering backlash that is spreading anti-gay bills across the country.

Republican-controlled legislatures have introduced more than 85 anti-gay bills in 28 separate states, according to the Human Rights Campaign, the largest LGBT-rights advocacy group in the US. New laws targeting gay couples have been passed in Indiana, Arkansas and Mississippi, with many other states attempting to follow suit.

On Monday, Apple’s openly gay chief executive, Tim Cook, sounded the alarm about the rash of new laws, which he described as contrary to America’s founding principles of freedom and equality. He likened the anti-gay surge across state assemblies to “whites only” signs in the days of racial segregation.

“We must never return to any semblance of that time,” he said.

Eunice Rho, advocacy and policy counsel for the American Civil Liberties Union (ACLU), said the volume of legislation coming out of state assemblies was “very high and very troubling”. She said the phenomenon was a direct response to the advances made by the LGBT equality movement that now stands on the verge of what is expected to be an historic US supreme court ruling extending constitutional protections to same-sex marriage.

“A lot of what we are seeing now is the rewards of our success. We see this for what it is – it is Plan B: an attempt to erode the gains that have been made towards marriage equality and LGBT equality overall,” Rho said.

Shannon Minter, legal director of the National Center for Lesbian Rights, said civil rights and LGBT groups were working closely together in a concerted effort to block the bills before they ever reach the statute books. Where new laws have been enacted, litigation would be considered, but only as a last resort Minter said.

“It’s so much better to stop these discriminatory moves before they become law. Litigation is a very expensive, time-consuming and uncertain way to fight back.”

The discriminatory bills have come in a variety of guises. Some like those in Alabama, Florida and Michigan would allow officials to turn away gay and lesbian couples seeking to adopt or foster children.

Republicans in other states such as Oklahoma are trying to allow gay conversion groups to flourish by protecting gay-to-straight “therapy” groups from legal action. Florida has gone another route still, focusing its efforts on transgender individuals.

But the most common form of the backlash has come in a spate of bills known as Religious Freedom Restoration Acts (RFRA), that seek to claw back some of the ground lost to same-sex marriage by allowing businesses and individuals to refuse services to gay and lesbian couples on grounds of religious conviction. A law of this sort was attempted by Arizona but vetoed by the then governor Jan Brewer last year, following a rebellion by local business leaders.

Arkansas is reaching the final stages of a similar “religious freedom” bill. Last week Indiana’s governor Mike Pence signed into law its version of RFRA, prompting a blizzard of largely adverse reaction from activists, business leaders, religious groups, media outlets and sporting leagues. The furor has put Pence on the defensive, forcing him to offer a possible supplementary bill that would “clarify” the purpose of the new law.

Minter said that the response had been overwhelming. “I’m feeling very optimistic after what has happened in Indiana,” he said. “There has been a huge public outcry coming from all quarters and that’s a testament to the highly structured network that has been created that can get the word out quickly.”

But challenges remain. As Arkansas pushes ahead with its own variation of RFRA, the Republican-held legislature has already passed a law that would leave LGBT people vulnerable to discrimination anywhere in the state.

SB 202 prohibits any city, town or county in the state from framing its own local ordinances relating to discrimination. The law does not specifically mention the LGBT community, but given its timing just before the US supreme court hears aural arguments in its review of gay marriage on 28 April, the impetus of the act is widely assumed to be in that direction.

SB 202 declares an “emergency” that it says must be addressed in the name of “the public peace, health and safety”. It says that it is “immediately necessary to create uniformity regarding discrimination laws across the state” – which is ironic because Arkansas at state level has no anti-discrimination laws relating to gay people.

In effect Arkansas, as well as Tennessee and West Virginia, which are pursuing similar laws, are saying that discrimination against the LGBT community must be allowed to take place in every corner of their territory.

Even where bills are defeated, there is no guarantee that they will not return. Republican representatives in Maine tried to pass an RFRA bill last year but were forced to drop the legislation in the face of widespread opposition.

Now a coalition of groups in the state is gearing up for what is expected to be a renewed attempt to pass the law. “We anticipate they will make another attempt, and we’ll be ready for it,” said Ben Klein, a senior attorney with Gay and Lesbian Advocates and Defenders in Boston.

Klein said he was confident a revived bill would be defeated a second time. “We have very strong arguments that these laws are contrary to the country’s values of individualism and equal protection in front of the law. They are bad for business and have many untold consequences.”