Boris Johnson is heading for a clash with business leaders after declaring London has "nothing to fear" from leaving Europe.
The mayor will launch a report on Britain's future relationship with the EU in a major speech tomorrow.
But he appeared to leak key findings in his monthly radio phone-in programme on LBC.
The mayor backs the Prime Minister's calls for a new deal with Europe but thinks withdrawal is a viable option.
The mayor's Eurosceptic views put him on a collision course with London businesses.
A recent poll by the London Chamber of Commerce and Industry concluded 75% of firms believe a full withdrawal from Europe would "negatively impact on the UK economy".
And a recent report from business organisation London First revealed 30-40% of London's exports are to the EU