and left the company after their earn-out period ended late last year.
Now Murphy plans to take his experience in building a membership website and apply it to .
It already has 500,000 regular users and 1,300 partner retailers.
Members have the incentive to receive cashback on online purchases ranging from their weekly Tesco grocery shop to the new iPhone from the Apple Store.
Retailers pay Quidco for delivering sales, and Quidco passes this commission on to its members, who pay a £5 annual membership charge, which is deducted from their earnings.
It also makes money from partnerships with retailers wanting to feature special deals on the site, although it does not carry any advertising.
Murphy, who is taking the role of executive chairman, aims to quadruple sales generated for its retail partners from £250m annually to £1bn.
Murphy said: "Already half a million savvy shoppers are benefiting from using Quidco but the fact remains that fewer than one in 10 people in Britain have heard of it.
"So my mission is to turn shopping's best kept secret into the way millions of people in Britain save money every day."
Launched by Paul and Jennifer Nikkel in May 2005, Quidco is now the market leader, and is double the size of its nearest competitor according to Hitwise.
Prior to joining Friends Reunited, Murphy was chief operating officer at the Financial Times.