Sportswear tycoon Johan Eliasch, one of the richest men in Britain and among the richest Swedes, is to advise Brown on environmental matters, according to the BBC.
Eliasch is well known for his commitment to environmental causes. He last year paid £8 million ($16 million, 110 million kronor) for 160,000 hectares of Amazon rainforest, stopping all logging operations on the land.
His recruitment by Brown's Labour government has caused raised eyebrows in British politics - Eliasch had previously been a lifelong Conservative. He had been a member of the Moderate Party's youth wing in Stockholm, and had more recently lent £2.6 million to David Cameron's opposition Conservative Party in the UK.
British reports say Eliasch was disappointed by Cameron's moves to take his party further to the right.
Eliasch told the BBC that he no longer wanted to be involved in any political party. His role as a climate-change advisor to Gordon Brown was a non-party matter, he said.
Born into a family of wealthy Swedish industrialists, Eliasch has made a fortune of his own as head of Dutch sportswear business Head. The Sunday Times Rich List puts his fortune at £355 million.