Oasis stalwart Sharon O'Connor has been promoted to managing director, a post created to free chief executive Derek Lovelock to head the newly expanded group.
Lovelock said: 'The move reflects the size of Oasis, making sure it has the management team and the resources it requires to take it on to the next level. That's giving it a dedicated managing director, which also prepares Mosaic for the bigger grouping.'
O'Connor was previously joint managing director of Oasis's Chinese venture and will be appointed to the Mosaic board. Lovelock revealed plans to bring operations at the 425-strong chain in line with high street competitors. He said: 'We all recognise there are changes in the industry at the moment - everybody's changing terms and chasing margin. The business has grown and it's time to have a good look at it.'
Several high street fashion groups - including Marks & Spencer, Matalan and Arcadia - have tightened supplier payment terms in the past year amid a tough consumer environment.
Jane Woolf, a veteran at Oasis, has been appointed product director and will oversee the review of the retailer's sourcing, trading and supply chain strategy, which will be implemented over the next 12 to 18 months.
Mosaic has also shaken up the tier of management reporting to O'Connor and Lovelock. Nadia Jones, previously Oasis design director, will work with Lovelock to develop Mosaic's growth strategy through new projects. 'These can be new product areas for existing brands or totally new concepts,' said Lovelock.
Former Karen Millen product development head Lisa Taylor will assume Jones's role. Her remit will include improving the fashionability and aspirational position of the brand.
Mosaic - which also operates Karen Millen, Coast and Whistles - is to merge with fashion group Rubicon, subject to due diligence. The£353 million deal will make it the second-largest fashion retailer in the UK behind Arcadia.
Oasis operates almost 300 stores in the UK and 130 outlets overseas.