New Zealand's main opposition party has proposed a broadening of the Reserve Bank of New Zealand's targets and the addition of a variable compulsory savings rate to take pressure off interest rates and the New Zealand dollar.Labour Finance spokesman David Parker announced the party's policy this week ahead of the September 20 general election, which is expected to be a tight contest between the governing centre-right National-led coalition and the opposition centre-left grouping of Labour, Green and New Zealand First parties.Parker proposed an Australian-style compulsory savings scheme, where the employee contribution rate could be increased by the Government as an alternative to raising interest rates."The next Labour Government will upgrade the Reserve Bank Act by broadening its objective and giving it a new tool that will enable it to tackle our high overvalued dollar, help create jobs and keep interest rates low," Parker said in a speech to a business audience in Auckland on Tuesday.The Reserve Bank Act would be changed to include a long-term target of achieving a current account surplus, Parker said. Currently the bank is focused on price stability, but a changed act would include the target of maintaining price stability "in a manner which best assists in achieving a positive external balance over the economic cycle."Parker said a Labour Government would make the current opt-out KiwiSaver pension scheme compulsory, with the current 6 per cent contribution rate rising at a rate of half a per cent or one per cent per annum over time to a total of 9 per cent."Rather than increasing or decreasing interest rates, the Reserve Bank could ask the government to vary Kiwisaver contribution rates, within a defined range," he said.Parker also suggested the bank could use its current macroprudential tools to help achieve its wider objectives. He cited the potential to use changes in capital requirements for different classes of lending to slow credit growth or reduce currency pressures, rather than just to improve financial stability.He said the monetary policy changes would work in tandem with already announced Labour plans to impose a Capital Gains Tax, to ring-fence losses from investment property from other income, and for the Government to build 100,000 new homes over 10 years to contain house price inflation.