In an attack on accountants and tax advisers for "peddling lies" about Labour's plans, he read the riot act to his Shadow Cabinet colleagues, reminding them not to engage in public speculation about tax.
Leading firms of accountants, including KPMG and Ernst & Young, recently advised clients to take action to avoid possible higher rates of tax on incomes above pounds 40,000 a year under a Labour government. "People would be better gambling on the lottery than on the random advice coming from some of these sources," Mr Brown said.
Brian Mawhinney, the Tory party chairman, said: "If Mr Brown doesn't like it he has a simple remedy - he should publish the tax plans and be damned."
Douglas Fairbairn, national tax partner of Ernst & Young, responded to the criticism by saying that, without firm tax proposals from Labour, "some degree of educated guesswork is inevitable".
"Until Labour publish firm proposals, we have a duty to our clients to take Labour's published statements and try to make sense of them. Some degree of educated guessing is inevitable and we haven't disguised that."
Mr Brown's speech, to a business audience in London, was also aimed at his own party. Tax advisers' guesswork appeared to be supported by remarks from Clare Short, Labour's transport spokeswoman, and John Prescott, deputy leader, in recent weeks.
Ms Short and Mr Prescott were backed by Roy Hattersley, former deputy Labour leader, who said their comments on tax "were blown up into stories in part because of the instinctive malice of some newspapers but Labour's reluctance to talk about tax provided them with the opportunity."Reuse content