By Jill Serjeant

NEW YORK (Reuters) - Shows like "Transparent," "Doubt" and "Queen Sugar" have helped boost the number of lesbian, gay, bisexual and transgender characters on U.S. television to a record high, a report from the advocacy group GLAAD said on Thursday.

GLAAD said the number of transgender characters had doubled to 16 this year. There was also a record high percentage of black characters on broadcast television, thanks mostly to shows like hip hop family drama "Empire," action-packed drama "Luke Cage," comedy "black-ish," and crime series "How To Get Away With Murder."

The "Where We Are on TV" report looked at diversity on broadcast, cable and streaming services for the 2016-17 television season.

It found a total of 278 LGBTQ regular and recurring characters across all platforms, the highest since GLAAD started tracking such numbers 20 years ago.

"While it is heartening to see progress being made in LGBTQ representation on television, it’s important to remember that numbers are only part of the story, and we must continue the push for more diverse and intricate portrayals of the LGBTQ community," GLAAD President Sarah Kate Ellis said in a statement.

GLAAD said some TV characters and storylines still portrayed the LGBT community in a negative or stereotypical way, but noted that television was far ahead of movies in terms of representation.

One area of disappointment for GLAAD was the high number of lesbian characters being killed off. The report said more than 25 lesbian and bisexual female-identifying characters have died on scripted TV and streaming series since the beginning of 2016 - most of them violently - a move it said "sends a dangerous message to audiences that LGBTQ people are secondary and disposable."

GLAAD said it was looking forward to upcoming shows "Doubt," starring transgender actress Laverne Cox as a lawyer, and LGBTQ inclusive series like "American Housewife," "Designated Survivor," "Conviction, and the miniseries "When We Rise" which will chronicle the history of the gay and lesbian movement.

(Reporting by Jill Serjeant; Editing by Lisa Shumaker)