Osborne said that the OBR "correctly stay out of the political debate and do not assess the long term costs and benefits of EU membership".
However he quoted the OBR as saying:
"A vote to leave in the forthcoming referendum could usher in an extended period of uncertainty regarding the precise terms of the UK’s future relationship with the EU.
"This could have negative implications for activity via business and consumer confidence and might result in greater volatility in financial and other asset markets”.
Citing a number of external reports, the OBR says:
“There appears to be a greater consensus that a vote to leave would result in a period of potentially disruptive uncertainty while the precise details of the UK’s new relationship with the EU were negotiated.”