One well-known, one not so well-known, and one rising star
First, the most famous of the three. Paul Krugman is a US-based Professor of Economics, probably best known for having been awarded the Nobel Prize in Economics in 2008 for his work on international trade. He strongly opposes austerity, and has written several articles dealing specifically with British fiscal policy.
Must-read: The Austerity Delusion (Guardian, Apr 2015)
Simon Wren-Lewis is a Professor of Economics at Oxford University, specialising in fiscal policy. He blogs at Mainly Macro, and has coined the term "mediamacro" to describe the fallacious economic ideas that pervade popular discourse here and in the US.
Must-read: Mediamacro Myths: Summing Up (Mainly Macro, Apr 2015)
Benjamin Studebaker doesn't have the academic credentials of the two above, but what he does have is a gift for synthesising and communicating economic data. His comprehensive critique of the coalition's economic record was widely shared before the election, and I for one hope he has started as he means to go on!
Must-read: For the love of God, please stop David Cameron (Benjamin Studebaker, May 2015)