Brexit has forced the European Union to rethink its flagship capital market union (CMU) project and urgently look for ways to create an alternative financial market to London, according to a draft EU document seen by Reuters.

London is the bloc's biggest financial market by far but will be outside the EU from 2019, posing a challenge to the CMU project, which had already begun to flag before last year's referendum in Britain.

"The CMU reform programme must be updated so that it can meet the challenge of creating a more autonomous capital market for the EU-27 economy," says the document, written by the European Commission, referring to the remaining EU member states.