Alex Depledge, the Treasury's entrepreneurship adviser, is resigning and will leave on Thursday 29 October, the day after the Budget, the BBC reports.
The BBC describes her departure as a blow to the Chancellor John Healey's Budget preparations.
The same BBC report says the Chancellor will announce more support for small breweries on Wednesday. The Treasury said he wants "to turn the tide for our pint producers".
No measure or cost for the brewery support has been given. Until it appears in the statement, it remains a pre-Budget briefing.