A HASHTAG calling Boris Johnson a coward has started trending online ahead of a Channel 4 debate about climate change.

#BorisTheCoward was tweeted thousands of times following news that the PM was ducking out of the hour-long Emergency On Planet Earth debate, which include Nicola SturgeonJeremy Corbyn, Jo Swinson, Plaid Cymru's leader Adam Price and Green co-leader Sian Berry.

Nigel Farage also refused to appear on the show, which may be the first television appearance he has turned down in recent history.

Leaders will take questions from presenter Krishnan Guru-Murthy, who is likely to cover climate change, renewable investment and greenhouse gas emission targets.

Guru-Murthy said: "This debate has been called for by hundreds of thousands of people from all sorts of different walks of life."

The hashtag, which started trending on Thursday morning, also came off the back of news that Johnson had so far failed to set a date to be interviewed by the BBC's Andrew Neil, despite his opponents doing so.

Here's what some other Twitter users had to say: