Nobel laureate Angus Deaton and bestselling author Thomas Piketty joined more than 300 fellow economists in arguing there is “no economic justification” for tax havens as policy makers prepare to meet in London for anti-corruption talks.

In a letter organized by the charity Oxfam, the economists said “territories allowing assets to be hidden in shell companies or which encourage profits to be booked by companies that do no business there are distorting the working of the global economy.”

Such offshore holdings undermine the ability of governments to collect taxes, and politicians should respond by requiring companies to report taxable activities in every country they have operations in.

The letter was released as tax havens receive fresh focus in the light of the release of the so-called Panama Papers, millions of legal documents related to secret shell companies. U.K. Prime Minister David Cameron will host a summit in London on Thursday aimed at beating corruption.

Other signatories of the Oxfam letter included Olivier Blanchard, the former chief economist of the International Monetary Fund, and Jeffrey Sachs, director of Columbia University’s Earth Institute.