The phrase was coined by White House staffer Kellyanne Conway to defend press secretary Sean Spicer's blatant lies about the attendance numbers at Donald Trump's presidential inauguration in 2017.

Plain English executive director Neil James said the much lampooned phrase stood out in a post-truth period when global politics took an Orwellian turn.

"This outrageous take on dishonesty was our clear winner in a decade that saw democracy decline," Dr James said in a statement on Tuesday.

"Politicians are known for obfuscation, but 'alternative facts' was particularly worrying.

"It suggests our elected leaders can be right even when they are factually wrong. That sets a dangerous precedent for democracy."

Since 2010, the Plain English Foundation has curated an annual list of the worst words and phrases to highlight the importance of clear language.

Previous winners over the decade include corporations indulging in doublespeak.

Orica referred to chemical leaks as 'fugitive emissions' while Volkswagen hid behind 'possible emissions non-compliance' when it cheated on environmental tests.

The notable corporate trend of the decade was the way corporations spoke about job cuts when they had to fire staff.

In 2018, the ABC won the annual gong for using 'external career development opportunities' to discuss firing staff.

The decade also spawned an impressive collection of Frankenwords, as brands vied to attract consumer attention.

KFC's Goodification was an early winner, and honourable mentions went to Sportsbet for Merry Puntmas and Tourism Australia for its recent philausophy.

"At best, these non-words are ugly and hard to make sense of," Dr James said.

"At worst, they imply junk food is healthy and gambling is as special as a religious and family holiday."

Celebrity speak and popular culture didn't disappoint either.

'Conscious uncoupling' was the 2014 winner when Gwyneth Paltrow used the phrase to describe her separation from husband Chris Martin.

The lists often rounded out with a mixed metaphor and non-apology, which captured some of the most mealy mouthed manglish of the decade.

The foundation also released its 2020 list of worst words and phrases, with COVID-19 generating many new words.

The year's worst winner - 'vertical consumption' - was a roundabout way of saying you can drink while standing.

Australian Associated Press