A Republican super-PAC that aims to back candidates who support same-sex marriage has received $2.75m (£1.64m) in donations so far in 2014.

The surge in funding to American Unity PAC is the group’s highest recorded. The group took in just $260,000 (£155,000) in all of 2013.

According to the Washington Post, almost all of the funding came from two sources, GOP donor Paul Singer, who gave $1.7m, and billionaire investor Seth Klarman, who gave $1m.

Singer also gave his backing to a bill to outlaw anti-gay workplace discrimination, alongside several other high profile Republican donors.

A poll recently found that a large majority of young Republicans are in favour of same-sex marriage despite their party’s opposition, with 61% of Republicans under 30 in favour.

At the weekend, the Nevada Republican party voted to drop opposition to same-sex marriage from its state platform, signalling a change in direction from the GOP.

State party Chairman Michael McDonald had said: “I think it was about inclusion, not exclusion. This is where the party is going.”

There are currently no gay Republican members of Congress, but this year three gay candidates are running in priority midterm races for the party.