It started as some gentle ribbing about who would have the better-selling autobiography by the weekend.
But a Twitter exchange between Lord Alan Sugar and Chris Evans soon descended into a bitter tit-for-tat with personal insults being traded.
In a conversation about how many copies each they had shifted so far, Lord Sugar claimed Evans had overtaken him in the book charts last weekend solely because people who'd wanted to buy his had been snowed in - and bizarrely said only people who worked in shops had bought the Radio 2 DJ's tome.
Evans's Memoirs Of A Fruitcake sold more than Lord Sugar's What You See Is What You Get according to book charts last week.
Lord Sugar wrote: 'u only got there as my readers could not get to the shops due to snow . Your readers work in the shops.'
A perplexed Evans then retweeted Lord Sugar's assertion and added: 'Is @Lord_Sugar saying that no one who works in a shop should read his book ? What a bizarre message for a retail entrepreneur!
'Without shops, the people that work there and consumers that spend their cash there @Lord_Sugar would still be that miserable Alan bloke.'
But he was then accused by the Apprentice star of 'slagging him off.'
Lord Sugar hit out saying: 'omg the moral stance from someone who pinches fellow bbc colleagues jobs poor Wogan and Chiles.'
He then also kept addressing Evans by the name 'Ginger' and accused him of being a drinker again, saying: 'I am worried u might take my role in the apprentice. New format 16 people battle it out to find Britain's biggest boozer.'
He added: 'You are mixing me up sunshine never been in retail in my life. Hope facts in your book more accurate.'
Lord Sugar also involved their mutual 'friend' Piers Morgan in the row, Tweeting to him: 'facinating (sic) thing twitter your mate @achrisevans tells everyone to follow u and slags me off and my followers go up.'
He added To Evans: 'Ginger, my followers are going up since you mentioned my name: cheers... why are you not at Piers CNN bash? No invite? What a pal!!!'
Lord Sugar has a bet on with Britain's Got Talent judge Morgan as to who can get the most Twitter followers by Christmas day.
The loser has pledged to pay ÂĢ5,000 to Great Ormond Street Hospital.
Evans said this morning he was pulling out of the exchange, with one last salvo addressed to Lord Sugar, saying: 'Ha ha. You've finally lost the plot ! Glad I was here to witness it.
'Trying to squirm out of his tasteless remark disparaging the nations shop workers yesterday.
'I'm out of The @Lord_Sugar nonsense. His joke valve has gone haywire. Normal service resumed. Merry Christmas to one and all. Ho ho ho.'
Lord Sugar's spokesman said they would not be commenting on the row when contacted by MailOnline. Last month, The Amstrad boss was involved in a Twitter spat with TV presenter Kirstie Allsopp.
Evans's people have yet to reply.
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