LONDON — U.K. pubcaster Channel 4 attracted more than 900,000 viewers at 10 p.m. on a Monday to “Sex Box,” which featured three couples having sex in a “box” on stage, and then got them to talk about it afterwards with a panel of experts. But the nation’s TV critics disapproved — not because of the sex, but because they thought the show was boring. And many viewers were left feeling embarrassed and confused.

Although the sex on the show was not actually seen or heard — it took place in a sound-proofed room, whose walls were opaque — it still managed to provoke howls of outrage before it aired, and even warranted a discussion on “Good Morning America.”

The show is part of a season of programs that sets out to reclaim sex from the porn industry by allowing people to talk candidly about it in an adult way. But the TV reviewers were not amused.

Ed Cumming from the conservative Daily Telegraph said: “‘Sex Box’ was one of the worst TV programs I have seen in a long time. From concept to execution, it was a combination of gimmick, prurience, exploitation and dullness.”

Sam Wollaston in the left-leaning Guardian newspaper added: “A gimmick, then, which might have been more excusable if it had made for great television. But it wasn’t.

“Maybe it needed some audience participation (in the discussion, in the sex too, why not?), perhaps a disgusted of Tunbridge Wells voice in there. Yes, I’m saying I was a bit bored. Boring-snoring sex.”

Christopher Stevens in the Daily Mail wrote: “Everything about ‘Sex Box’ was badly devised. Agony aunt Mariella Frostrup got all girly and giggly with the couples before sending them into the shed; the studio audience twiddled their thumbs while a trio of sexologists explained that the British don’t usually like talking about you-know-what; and then the couple emerged, and everyone got embarrassed.”

Many viewers said via Twitter that they found the show confusing and embarrassing. One wrote: “What is this program? I am dying. Awkward is an understatement.” Another complained; “#sexbox Is this actually happening? Who? What? Where? When? Did this ever get commissioned!”