Seymour joined the Perth-based utilities giant in 2006 to set up its water division and will become head of market development at Business Stream, where he will be charged with winning clients.
A draft water bill currently travelling through the Westminster parliament would allow all non-household customers in England to choose their water supplier, a measure introduced in Scotland in 2008.
Since then, more than 40 per cent of the Scottish market has gone out to tender.
Mark Powles, chief executive of Business Stream, said: “Many of our customers in Scotland have told us they want us to provide the same service in England, and having someone of David’s calibre on board gives us a very strong offering when full competition starts in England.
“We are laying the groundwork for growth in England and see great opportunities there to take the model we’ve created in Scotland and use that to bring the benefits of competition to businesses across Scotland and England.”
Prior to his role at SSE, Seymour spent five years at United Utilities, latterly as project manager responsible for delivery of the Thames Gateway project, an economic development scheme launched in 2007 to regenerate parts of Essex, Kent and London.
Seymour admits that he faces a tough challenge. “When the market opens, it will be extremely competitive,” he said.
The non-household sector in England is estimated to be worth £2 billion a year and the House of Commons environment, food and rural affairs committee believes it could take three years to open the industry up to competition.
At present, 21 companies have regional monopolies over domestic and non-domestic customers in England.
Business Stream currently serves more than 90 per cent of Scotland’s £360 million non-household market.