The Agriculture Minister defended the overhaul of the 37-year-old system as a "major step forward" which marked a "radical change in direction". The reform, yet to be agreed by finance ministers at an Ecofin meeting, will lead to cuts in subsidies on beef, dairy and cereals production, with dairy quotas phased out in 2006.
However, the deal, struck after all-night negotiations, has been rejected by Tony Blair as "not good enough".
In a Commons statement, Mr Brown acknowledged it would take years for the full benefits to come into force, but said the reform would be good for British consumers, farmers and the environment. "The outcome represents a radical change in the direction of the CAP for which the Government has been pressing strongly."
It had been achieved despite a reluctance to reform on the part of several countries, he added. The British rebate had never been under discussion during the negotiations.
Shadow Agriculture Minister Tim Yeo said despite Mr Brown's "rather extravagant" claims, the deal was unsatisfactory. "Claims of a windfall for consumers are hopelessly premature," he said.
He added that the deal had failed to reform the CAP in the promised way and the cost of it would now rise even further than originally feared.