By Emmanuel Jarry and Annika Breidthardt

PARIS/BERLIN (Reuters) - Germany rebuffed French President Nicolas Sarkozy's call for a debate on the European Central Bank's role in promoting economic growth, reaffirming on Monday its attachment to the ECB's independence.

The conservative Sarkozy, trailing Socialist challenger Francois Hollande in opinion polls a week before the first round of voting, said at a campaign rally on Sunday that Europe needed to rethink the ECB's a role in supporting economic activity.

"If the ECB does not support growth, we will not have enough growth," he told some 100,000 supporters in Paris' Place de la Concorde. "It's our duty to reflect on this issue. We cannot have taboo subjects."

Aides said Sarkozy wanted a discussion of whether the central bank could better steer its exchange rate policy to favor euro zone exports and was not pushing for a change in the ECB's treaty mandate beyond maintaining price stability.

German government spokesman Steffen Seibert, asked about Sarkozy's comment, told a regular news briefing in Berlin: "It is the core belief of the federal government ... that the role and office of the ECB be independent of encouragement and assistance from politics. And that's well known in Paris."

French analysts brushed off the president's remark as campaign rhetoric designed to attract nationalist voters, as he had done during the 2007 election race.

Hollande has called for the ECB's mandate to be revised to add a responsibility for promoting growth, while radical presidential candidates have said the central bank should be allowed to lend directly to governments.

One Sarkozy aide, asking not to be quoted by name, said the president knew he would have "no chance" of getting the ECB's mandate changed to include provisions for supporting growth.

"What we want is for there to be a dialogue between the economic government (of Europe) and the ECB on all important issues and in particular exchange rate policy," the aide said.

French governments have consistently pressed for a cheaper euro to promote the country's exports of aircraft and cereals, to no avail. But the refrain strikes a chord with voters.

Jean-Francois Cope, secretary-general of the ruling UMP party, said Sarkozy would seek a broad debate on the ECB's role if he wins re-election on May 6.

"After the election it will be one of the issues that deserves to be dealt with, even if for now it's premature to talk about what kind of format the talks could take," Cope told a meeting with foreign media.

"We could bring up the role of the ECB with our European partners after the election, for sure," he said.

PUNCHING BAG

Politicians have long sought to score points with voters by suggesting the ECB's mandate should be extended to bring it more in line with that of the U.S. Federal Reserve, which has a double mission to ensure price stability and full employment.

Berlin believes capping inflation is the best way to promote growth as it keeps down medium and long-term interest rates.

Sarkozy's comments ran counter to an agreement he made with German Chancellor Angela Merkel last November to cease commenting publicly on the ECB's role and responsibilities.

"Just like the French government we see the need for sustainable growth in Europe and have taken a number of initiatives with the French government for exactly that reason," Merkel's spokesman Seibert said.

Sarkozy has clashed with Berlin during his time in office over the ECB's role, having pushed for it to take a more direct role in resolving the euro zone's debt crisis.

The Frankfurt-based ECB defines and implements euro zone monetary policy, conducts foreign exchange operations and looks after the foreign reserves of Europe's central banks.

Hollande's election manifesto also calls for the bank to have a role in encouraging economic growth in the euro zone, and he also wants a recent European pact on budget stability renegotiated to add pro-growth clauses.

Etienne Gernelle, editorial director of weekly news magazine Le Point, told BFM TV that he saw Sarkozy's comments on the ECB as pure electioneering, adding that all the election candidates were being irresponsible by using Europe as a punching bag.

"They all talk nonsense on Europe because it's easy, it's not there to defend itself," he said. "It's totally irresponsible on the part of all French politicians.

(Reporting by Emmanuel Jarry, Yann Le Guernigou and Nick Vinocur in Paris,; Annika Breidthardt in Berlin; Writing by Catherine Bremer; Editing by Paul Taylor)