For Nick Clegg, I have a plea. For the nation, I have an apology.

Firstly, to the well-dressed people of Great Britain, I would like to repent. My confession: I was one of the first journalists in the country to spring the 21st Century's greatest crime against fashion on to an unsuspecting public.

Back in 2010, writing a feature in the Daily Mail, I had to explain to readers what they were.

"Not only is this full-bodied fleece zipped from crotch up to forehead, it is also the height of fashion," I enthused. Nowadays, I need not bother - the onesie is ubiquitous.

The Independent's media column mocked my piece at the time, because it was published on the same page as one by Angela Huth, novelist and friend of Princess Margaret who, according to The Indie, 'dashed off a rant' about the 'ghastly modern world', headlined: 'Sorry, but everything I love is old-fashioned.' Oh, the irony.

Huth sighed: "I can't imagine what it must be like to be spurred by a desire for so-called fashionable things. It must be exhausting to be compelled to keep up with trends."

I must admit that I was sceptical they would take off as a trend at all. Yes, they were and are uber-comfy. And I later met the three young Norwegian inventors of the 'original' OnePiece, a lovely bunch of guys, who I'm sure had no ill intent. But they are just so un-British. However you wear one, it makes you look like a moron. Most awful of all, though, the toggle on the zip pokes out at crotch level. It's frankly embarrassing. I'll admit I love wearing mine behind closed doors, but I'm mortified if the postman sees me in it.

Moreover, I couldn't believe anyone would pay £120 for the OnePiece I was sent to review. How wrong I was. Within a few weeks of my article, the company had bumped the price up to £140-plus for my Scandi-print onesie. And sales have been booming ever since.

We read this week that 'barnstorming' demand for onesies has helped Debenhams smash its Christmas sales record, with shelves 'completely cleared'. Asda stockpiled a million over the festive season and Marks & Spencer sold more than two a minute. And they have become such a cultural phenomenon that Newsnight saw fit to send its culture correspondent Stephen Smith to go and report on them.

What's more, the trend for infantile winter fashion has abounded in the wake of the fleecy adult babygro, which itself followed hot on the heels of the ridiculous Slanket, 'the blanket with sleeves'.

Now you can buy a Beard Head, a beanie hat with knitted beard and moustache attached. Or you can slip on a Sheebie. It may sound like a feminine hygiene device, but in fact it's a unisex scarf, hat and gloves in one.

However, my shame enveloped me like an itchy Primark all-in-one on Thursday when the deputy prime minister admitted to owning one while conducting a radio phone-in.

And not an understated or stylish one either à la Winston Churchill -- who wore an elegant pinstripe design during the war -- but a baggy and ghastly green 'Incredible Hulk' design. Mr Clegg said after his radio revelation: 'We are turning our attention to 2015 to the election campaign. We are all trying to finesse our key messages and as you know my philosophy which will underpin everything we say is that of the onesie nation.'

Boris Johnson has already boasted of possessing a Union flag one. And my sources tell me that Prince Harry and his clan love to wear onesies while clubbing at Whisky Mist. While his mother used to disguise herself in a brown wig to go out on to the streets of London unnoticed, I'm told Harry zips his onesie up over his face and parties on into the night.

Now we just need the Queen to slip on a diamanté all-in-one and our national humiliation will be complete.

One ray of light is that the prime minister hasn't owned up to the style sin yet -- his spokesman declined to comment. But then again, David Cameron has always kept shtum on the question of whether he was caught with cannabis at Eton, so maybe we shouldn't be so sure.

We already know the Cleggster is a man who is happy to put his pride on the line to affirm his political mission to the electorate.

He gave his consent for his auto-tuned 'I'm Sorry' dittie to hit the charts and has now signed himself up for a weekly radio grilling-by-the-people as part of what Alastair Campbell once dubbed a 'masochism strategy'. But, please, even Tony Blair would baulk at this.

So, I send the DPM a quiet but pleading invitation. Please return the offending garment to its packaging, stick with your lovely shirt and tie, and leave the term 'onesie nation' to die in the same corner as 'The Big Society' and 'we're all in this together'.

David Mellor never even wore his Chelsea kit during amorous encounters, and who knows if John Major is a Y-fronts man, but the toxic pictures have been immortalised.

Nick, you shouldn't be worrying about the next election, you should be worrying about your legacy.

We may quickly forget your soundbites and your policies. But the image of you trussed up and swaddled in a novelty baby outfit? That one's not just for Christmas, it will stick around for good.

View Etan Smallman's website at: www.etan.info

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