Kate Middleton's brother sells saucy cakes (4 PICS)

Little brothers have always been a source of juvenile humour - but this one really takes the cake. 

James Middleton, whose older sister is the Duchess of Cambridge, has launched a business specialising in cakes iced with smutty slogans.

The 24-year-old's edible designs cut a stark contrast with the Royal Family's famous sense of decorum, offering jokes about 'jiggly jugs', 'yummy bums' and 'wriggly willies'.

It's all a far cry from the eight-tiered confectionary masterpiece that was cut at his sister's wedding reception last year.

But the suggestion that his new business could embarrass the Royal Family were dismissed by Mr Middleton.

He said: 'They are clearly intended to be humorous and are clearly not intended to cause any offence as is quite obvious. 

'The Great British public is renowned throughout the world for its sense of humour and a cake design is hardly likely to cause it to lose it. We intend to embrace that sense of humour.'

Businessman: James Middleton, 24, now has four companies under his belt

Nice Cakes is one of four companies started by Mr Middleton, who claims to be a self-made man despite his royal links and his parents' success in the party supplies industry.

One design, called Stud Muffin, shows an image of a man and the words ‘A willy that wriggles and gives me the giggles’ and ‘A yummy bum for squeezy fun’.

Another Sexy Hubby cake reads ‘Buttox of steel for a squeezy feel’ and, next to an arrow pointing to the cartoon man’s crotch, ‘Weapon of mass seduction’.

A Wonderful Wife cake, which sells for £19.99, lists ‘Scrummy boobies that make my hands happy’ and ‘Sexy bum that wiggles when ironing’.

Other messages border on the abusive, with foul-mouthed greetings such as 'You greedy b******' and 'You're a t*** but I like you'.

Family firm: Nice Cakes is run from the same business park as Michael and Carole Middleton's company Party Pieces (pictured), near Upper Basildon, Berkshire

The Nice Cakes website allows customers to tailor cakes to their needs, completing joke templates with friends' and relatives' names or creating their own captions for old-fashioned photographs.

Mr Middleton said he is running the business independently of his parents' successful party supplies firm, but confirmed there are links between the two.

Orders are taken from the same Berkshire business park, while calls to Nice Cakes are routed through the switchboard for Party Pieces, which is owned by parents Carole and Michael.

Family ties: James Middleton with his sister the Duchess of Cambridge and Zara Phillips at a charity concert in 2007. He brushed off the suggestion that his risque cakes could embarrass the Royal Family

Mr Middleton said it was not 'uncommon' for businesses to outsource.

His first venture was the Cake Kit Company, after which he launched Nice Cakes, Nice Wine and Nice Group London.

The young businessman, whose parents bought him and his sister Pippa their £1.2million flat in London, says hard graft is the secret of his success.

Mr Middleton, who was educated at the £30,000-per-year Marlborough College and dropped out of Edinburgh University after just a year, has insisted that 'nothing is handed to anyone on a plate'.

Earlier this year he told the Sunday Times: 'I've won awards for my own efforts because I am young and good in my own right.

'It's not just because of my family that I've been getting attention. I want to be known for my own contribution, not for being a "relative of" - that's boring.'