One Republican lawmaker has broken ranks with his party to become the first to endorse an LGBT rights bill.

There is currently no federal US law prohibiting discrimination against LGBT people, meaning it is still legal to fire someone for being gay in a number of states.

A bill known as the Equality Act – which would outlaw discrimination and ensure a range of protections for LGBT people – was tabled by Democrats in Congress last year.

The bill has made little progress as Republicans currently control both Houses, and until this week not a single member of the Republican Party has stepped forward to back it.

However, Illinois congressman Bob Dold has broken ranks with his party to co-sponsor the legislation – becoming the first GOP lawmaker to do so.

The bill has won support from Barack Obama, Hillary Clinton, Bernie Sanders and large corporations including Apple – but even purportedly pro-LGBT Republican groups like the Log Cabin Republicans have declined to back it.

Declining to take a stance on the bill, the Log Cabin Republicans claimed it “shares hesitations” with lawmakers who have raised concerns about the impact on religious freedom.

But Congressman Dold said: “Illinois has a long and proud history of fighting for equal rights, and I am proud to continue this tradition by supporting the Equality Act.

“Engraved on the front of the Supreme Court is the phrase ‘equal justice under the law,’ but as long as any Americans can be legally discriminated against, there is not equal justice in this country.

“Congress must act to ensure that all Americans, including the LGBT community, are protected equally from discrimination under federal law, just as they already are in my home state of Illinois.”

He said the bill is “not perfect”, but added: “It marks an important first step in the process of crafting a bipartisan bill that ensures equal rights for all Americans while also fully protecting the religious freedoms our Constitution guarantees.”

The extreme polarisation on the issue shows the divide in party politics has grown since a similar bill, the Employment Non-Discrimination Act, in 2013.

Though ENDA was ultimately blocked by Republicans, at the time it picked up a handful of Republican co-sponsors – many of whom have since declined to back the vastly-similar Equality Act.