Britain's Financial Conduct Authority plans to publish comprehensive trading data for London-listed shares in an effort to counter what it sees as significant under-reporting of market liquidity that has contributed to companies choosing to list in the United States, the Financial Times reported on Monday. The FCA is considering collecting and releasing share-trading data from all venues, including exchanges, dark pools and off-exchange platforms, to provide a fuller picture of liquidity in UK markets.

Simon Walls, the FCA's interim director of markets, told the FT the regulator believes current liquidity metrics are misleading because they rely heavily on data from the London Stock Exchange's central limit order book, excluding many trades such as periodic auctions and transactions conducted on opaque venues. Between January and September last year, the FCA estimates around 270 million UK share transactions were recorded in central order book data, but total trading activity over that period appears to be roughly four times higher, the report said.

The regulator is consulting on the creation of a consolidated tape to combine all UK share trading data into a single stream, a project expected to be completed next year. In the interim, the FCA is in discussions with market participants on publishing aggregated trading data to bridge the gap, Walls said. The move comes as the UK seeks to revive capital markets after a prolonged slump in initial public offerings and several high-profile listings moving overseas.