Swiss exporters still need lid on franc - minister

* Swiss companies better prepared if cap should fall

* Up to SNB to decide when to give up franc policy

* Purchasing-power parity with euro will take time

ZURICH, Sept 30 (Reuters) - Swiss exporters need the central bank to defend the cap it imposed on the strong Swiss franc a year ago, even if they have become more efficient, Economy Minister Johann Schneider-Ammann was quoted as saying.

"The Swiss franc is still overvalued, perhaps no longer as strongly as in summer 2011. Export companies need the planning security of the minimum limit," Schneider-Ammann told SonntagsBlick newspaper in an interview.

The Swiss National Bank set a cap of 1.20 francs per euro a year ago to prevent the soaring safe-haven currency causing deflation and a recession.

Export-oriented Swiss industrial companies have started to recover from the ill-effects of the strong franc and are doing better now than at the start of the year, a study showed last week.

Schneider-Amman said that Swiss companies had used the protection of the cap on the franc to become more innovative and efficient. "They are better prepared should the safety net fall away," he said, "but the minimum limit is still needed, without any ifs or buts."

Asked when the SNB could give up the policy, Schneider-Ammann said that was a matter for the central bank, but noted that his concern was ensuring full employment.

Schneider-Ammann dismissed suggestions that the inflation differential between Switzerland and the euro zone meant that the 1.20 per euro limit would soon near purchasing-power parity.

"That will still take a long time. The inflation differential is about 2 percent. Purchasing-power parity is still 10 or more percent above the exchange rate," he said.

(Reporting by Emma Thomasson; Editing by David Goodman)