Citadel Securities, a unit of the Chicago-based hedge fund firm, will take a majority stake in Equiduct, the alternative share trading platform.

The move is aimed at turning Equiduct, launched in April, into a pan-European platform for share trading aimed at retail, or smaller, investors.

The idea is to replicate what Citadel has done in the US through its investment in Direct Edge, which has grown to become one of the top four exchanges in the US, along with NYSE Euronext, Nasdaq OMX and BATS Global Markets.

Equiduct was founded in 2007 by Börse Berlin, a small German regional stock exchange, with a 53 per cent stake. Jos Peeters, a Belgian venture capitalist and founder of the former Easdaq exchange, held 23 per cent with the rest held by Knight Capital and other investment banks, including Goldman Sachs.

Citadel Securities, a trading arm of its Chicago parent, will make a â??significant equity investmentâ?� in Equiduct, it said. Matteo Cassina, president of Citadelâ??s execution business in London, did not specify how much investment was involved, nor what the stake would be. But he said it would be â??enough to run the platform for the next couple of yearsâ?�.