Peter Power, Mandelson's spokesman, said: "This is a very considerable advance and it is a very substantial improvement and should inject important momentum into discussions in Geneva this week."
Ministers from 35 countries were launching a fresh bid in Switzerland to get the nearly seven-year-old Doha round of trade liberalisation talks back on track.
Developing countries Brazil, India and Indonesia poured cold water on the proposals and even Mariann Fischer-Boel, Mandelson's fellow EU commissioner, who holds the agriculture dossier, said of the proposal: "It's nothing new."
Anne-Marie Idrac, the French trade minister, said: "Was there new progress, new percentages? The answer is no. Peter Mandelson this morning had clarified ... what technical discussions have come up with - nothing more, nothing less."
Idrac said that the difference between the two figures were down to whether tropical products were included in the tariff cut calculations or not.
Meanwhile, Michel Barnier, the French agriculture minister, maintained that the EU was not budging on its position on agricultural trade.
He said: "Anyway, no state member of the EU would be ready to accept or to support a new offer on this question."
Earlier, Roberto Azevedo, one of Brazil's leading negotiators, said the number was a "consequence of the different numbers on which the EU had already agreed on among themselves. If they are proposing to cut, that's because they have the margin to do so".
Another member of the Brazilian delegation dismissed Mandelson's offer as mere "propaganda".
Proposals drawn up by Crawford Falconer, the WTO's chief agricultural negotiator, envisage sweeping subsidy cuts by rich Western countries, which have often been accused by developing nations of undermining free trade and pushing their farmers into penury.
The biggest subsidisers would make the biggest cuts, notably the EU, which would have to slash its payments to farmers by between 75 and 85 per cent.
Even before the latest 60 per cent proposal was made, Mandelson had described the 54 per cent cut as "painful" but a step Brussels was prepared to make to ensure a global trade deal.
Mandelson has been under intense pressure from EU member states, not least France which currently holds the EU presidency, to avoid giving too much ground on trade in agriculture.
Nicolas Sarkozy, France's president, has already accused Mandelson of overstepping his mandate and offering too much on agriculture subsidies.
Last week, John McGuinness, the Irish trade minister, said that the European Commission had gone "way too far" in its proposals.