Gay media watchdog the Gay & Lesbian Alliance Against Defamation (GLAAD) has launched a boycott campaign against real-estate mogul Donald Trump.

The 64-year-old Trump announced he's considering a run for the White House as a Republican during an appearance at this year's Conservative Political Action Conference (CPAC).

He's mounted a campaign to win over GOP voters in early caucus states New Hampshire and Iowa, which tend to prefer socially conservative candidates.

GLAAD says Trump's opposition to gay rights – he opposes both civil unions and marriage for gay couples – is behind their decision to ask members to turn their backs on the billionaire celebrity with political aspirations.

“Trump has taken to disparaging the families of gay and lesbian couples as a tactic to get attention for his candidacy,” the group says at its Tune Out Trump campaign. “Using Trump's own famous catch phrase, we would like to tell him, “You're fired!”

The campaign asks supporters to stop patronizing Trump establishments and television shows, including many buildings in New York City, casinos in Atlantic City, Fox News' Fox and Friends and NBC's Celebrity Apprentice.