FORMER N.Z. PREMIER CALLS FOR CHEAPER CURRENCY Former Prime Minister Robert Muldoon, an outspoken advocate of a managed float for the N.Z. Dollar, said the currency is at least 10 pct overvalued. Muldoon said in a speech last night the exchange rate should be around 48 U.S. Cents instead of the current 57 cents. "A reasonable value for the New Zealand dollar would be between 10 and 15 pct less and nearer 15 than 10. Perhaps around about 48 cents," he said. The Labour Party government removed exchange controls and floated the dollar two years ago when it was worth 44 cents. Muldoon has no rank in the opposition National Party, and party leaders, with an eye to general elections to be held by September, have rejected his calls for a managed float. He said the dollar was high because of "grossly excessive" interest rates for government stock. "I know of no other country which is implementing such a free floating policy," he added. "There is widespread agreement internationally that we have no alternative to floating currencies in the short to medium term. But we need more effective methods of managing them so as to limit the volatility which has caused so much concern and damage."