As one of the most photographed women in the world, fashion houses everywhere have been desperately fighting to get Kate Middleton into their creations.

But it seems Kate has now put an end to the frantic scramble – by clearly opting for Issa as her label of choice.

Prince William’s 26-year-old girlfriend is so closely affiliated with the label of Brazilian designer Daniella Issa Helayel that she is being treated as an unofficial muse.

Kate (left) leaves home wearing a sparkling blue number. Right: She steals the show at the Boodles charity ball in this £1,000 gown from Issa

Kate enjoys a VIP service from the firm and receives a complimentary wardrobe, with ‘bag-loads’ of Issa frocks being sent to her home.

‘Kate must have thousands of pounds worth of gifted dresses,’ said a source.

‘Issa is incredibly generous with her.’

Miss Middleton, who is known for her conservative yet stylish sense of fashion, chose an Issa outfit for Peter Phillips’s recent wedding, giving the brand invaluable publicity.

The eye-catching label is stocked at exclusive department stores including Harrods and Harvey Nichols, where the clothes retail from £400 for a short printed frock to £1,000 for a full-length gown.

Kate wore a white ‘Lucky’ dress from Issa to Wimbledon and has the style in every colour.

She was also draped in Issa when she appeared on the newspaper front pages in a stunning floor-length £1,000 coral gown at the Boodles charity Boxing Ball in June.

Fashion parade: Kate (left) steps out in an Issa printed dress and (right) in the 'Lucky'

Issa, which counts Madonna, Sharon Stone and Scarlett Johansson as clients, already has Harrods boss Mohamed Al Fayed’s daughter Camilla as its muse, but fashion sources say Kate is being seen as an ‘unofficial ambassador’.

Issa not only sends items to her Chelsea home, but Kate is also a regular client at its top-floor studios in Fulham, West London.

The source said: ‘Issa is one of Kate’s favourite labels and she is always at its offices choosing dresses. They also courier bag-loads of frocks to her house for her to try on in her own time. There is no limit on what she is allowed to take.

‘Daniella is a very flamboyant and lovely woman and an incredibly sharp business person. She knows the value of having celebrities step out in her label and Kate is very much on Issa’s A-list.

‘Kate gets sent so many clothes from other labels but many go back unworn. Her taste is quite classic and that’s why she goes for Issa’s print wrap dresses. She loves their floor-length gowns for black-tie events. She’s a size six and the dresses all look great on her.

Brazilian designer Daniella Issa Helayel

'She often lets her sister Pippa wear them, too. When Issa sent her the floor-length pink gown to wear to the Boodles do, she absolutely loved it and knew it would be a showstopper.

‘Kate actually loves all the attention of being photographed and she knew she’d steal the show in that gown. It worked – she outshone everyone in the room, even Chelsy Davy.’

Kate, who is currently helping with her parents’ internet party-planning business, has told friends she is keen to move into the fashion industry but she has yet to get a job.

She has not worked since she quit as a fashion accessories buyer for High Street chain Jigsaw last November.

The Queen has advised William that it would be favourable for Kate to have a career in place before they announce an official engagement.

It is understood that Kate has been offered an ambassadorial role by a London-based fashion house although Issa last night denied it had approached Kate to work for it.

Daniella Issa Helayel said: ‘Kate is not an ambassador for Issa. We love it and are very flattered that Kate wears Issa.

'We do have some friends in common, but that’s as far as it goes at the moment. She’s a private client and we never make any comment on our private clients.’

A spokesman for Clarence House declined to comment.