British Prime Minister Boris Johnson delivered an unconventional speech at the UN General Assembly on Tuesday that referenced "terrifying limbless chickens" and "pink-eyed terminators" but only mentioned Brexit once.

During a late-night, 20-minute address that drew laughs and baffled looks from delegates, Johnson struck a light tone on a serious subject as he warned of technology's capacity to control citizens.

He made no mention of Britain's highest court ruling earlier in the day that his decision to suspend parliament amid a Brexit impasse was unlawful.

The shock ruling plunged his plans to exit the European Union by October 31 into crisis and sparked calls by opposition MPs that he resign immediately.

At the UN, Johnson painted the possibility of a future where devices in every household "monitor your nightmares, monitor your fridge," and where smart cities are "as antiseptic as a Zurich pharmacy".

"'Alexa' will pretend to take orders but this Alexa will be watching you, clapping her tongue and stamping her foot," Johnson boomed, suggesting "there may be nowhere to hide".

"As new technologies seem to race towards us from the far horizon we strain our eyes as they come, to make out whether they are for good or bad, friends or foes.

"AI, what will it mean?" he asked of artificial intelligence.

"Helpful robots washing and caring for an ageing population or pink-eyed terminators sent back from the future to cull the human race?" Johnson pondered.

He went on to wonder whether synthetic biology could restore tissues "like some fantastic hangover cure" or "bring terrifying limbless chickens to our tables".

Johnson also referenced one of his favourite subjects, Greek mythology, by telling the story of Zeus punishing Prometheus by ensuring that an eagle ate his liver over and over again.

"This went on forever. A bit like the experience of Brexit in the UK if some of our parliamentarians had their way," he said, drawing laughs from the remaining delegates in the largely deserted hall.

The Conservative leader made an impassioned plea for technology to be a force for good and said he was optimistic it could "serve as a liberator and to remake the world wondrously and benignly".

He called on world leaders to agree to a set of guidelines to ensure that new technologies are designed ethically before inviting them to join him at a tech summit in London next year.

Whether Johnson is still prime minister then remains to be seen. Following his UN address he was due to fly back to Britain where a political storm awaits him, cutting his New York trip short.

He also poked fun at France during his speech, reminiscing about how when he was mayor of London the city had more Michelin stars than Paris.

"The French somehow rapidly recovered — by a process that I wasn't quite sure was entirely fair," he joked.