Conservative evangelicals have begun to hit back against an edict by the Obama administration directing every US public school district to allow transgender students to use lavatories that match their gender identity.

A letter signed by officials from the Education and Justice departments contains an implicit threat that schools which do not abide by the administration's interpretation of the law could face lawsuits or a loss of federal aid.

"There is no room in our schools for discrimination of any kind, including discrimination against transgender students on the basis of their sex," US Attorney General Loretta Lynch said in a statement.

According to Denny Burk, Professor of Biblical Studies at Boyce College, the undergraduate school of the Southern Baptist Theological Seminary, the move "represents the latest example of the Obama administration using a combination of policies, lawsuits and public statements to change the civil rights landscape for gays, lesbians, bisexual and transgender people".

Burk, a trenchant critic of liberalism, described the announcement on his blog as "jaw-dropping". He said: "This radical directive is a heavy-handed, unconstitutional overreach in order to force Americans to pretend that some boys are girls and some girls are boys. It is absurd and wrong."

He continued: "Transgenderism is a fiction that harms real people and undermines the common good. It is not good to treat boys as if they're girls nor to treat girls as if they're boys."

He warned the directive would "cause unrest and conflict all over the country. It is one thing for an individual to embrace a fictional identity. It is another thing for the federal government to coerce everyone else to embrace it too. This is far from over. Indeed the conflict has only just begun."

The Obama administration's announcement was made against the background of a bitter legal battle in North Carolina between the state legislature and the federal government.

Backers of the North Carolina law, which requires people to use public bathrooms that correspond with the sex on their birth certificate rather than their gender identity, say it will protect women and girls from predators. Transgender advocates say that claim is unfounded and ignores a modern understanding of people who identify with a gender other than the one assigned at birth. Burk's position reflects that of many Christian conservatives, such as Franklin Graham, who posted on Facebook: "I'm thankful to North Carolina Gov. Pat McCrory & other state legislators for standing up to the bullying and intimidation of the Obama Administration over HB2, NC's bathroom bill."