The stationery, homewares and lingerie retailers are owned by former Dragons' Den star Theo Paphitis, who has also tasked Haines with handling his personal profile and PR for his investments from the TV show.
Haines left Paddy Power last year to start his own consultancy, following 11 years with the bookmaking firm.
He has put his consultancy work on hold to take the new role, which he said was 'too good an opportunity to turn down'.
Haines takes over from Tina Fotherby, who left at the start of the year and was mainly responsible for publicity for Paphitis.
'I'm delighted to welcome Darren into our team to work across the three brands as we push them ever further into the national consciousness,' said Paphitis. 'PR is a powerful tool for business and for us in the exciting new opportunities ahead of us.'
Haines said he would carry out an overview of the brands before embarking on a PR strategy. He added that activity for Ryman and Robert Dyas, which Paphitis acquired last year, would focus on the brands' heritage and history.