The European Commission wants to cap agricultural aid under radical reform of the EU's long-controversial Single Farm Payment regime, an EU source said Thursday.

The reform is part of wider changes to the bloc's Common Agricultural Policy (CAP), which traditionally accounts for around 40 percent of its annual spending of nearly 140 billion euros.

Under plans for a new capping system to even-out subsidies, payouts to farmers would not be allowed to exceed 300,000 euros ($424,000) per year.

In addition, levies would be applied progressively on all payments exceeding 150,000 euros in what the commission said is a bid to make the system fairer.

The idea which still needs approval of the executive commission would take into account the number of paid farm employees so as to encourage employment.

Farm aid tied to environmental improvements, on the other hand, will be exempt from caps, with incentives to diversify land use.

EU farming commissioner Dacian Ciolos is due to present his plans to reform the CAP on October 12, for subsequent approval by EU member states and the bloc's parliament.