The average American family spends about 40 percent of its income paying local, state and federal taxes, prompting two Republican congressmen Saturday to propose a constitutional amendment that would make it harder to raise federal taxes in the future.

Reps. Joe Barton, R-Texas, and John Shadegg, R-Ariz., back an amendment that would require a two-thirds vote of both the House and the Senate to enact any new taxes. Currently, tax bills need only a simple majority plus one vote to be enacted."Taxes are at a record peacetime high, and the president's new budget plan proposes raising federal taxes to almost 21 percent of the average family's income," Barton said as he and Shadegg delivered the Republican response to President Clinton's weekly radio address.

"A tax increase that passes with a two-thirds vote in each house has demonstrated much more support among the American people, and that clear support should be required from both Congress and the American people before we start increasing tax bills again," he added.

Shadegg said his home state is a case study in the effectiveness of such an amendment. Arizona voters passed one in 1992, and today, the state remains one of the lowest-taxed states in the nation. Thirteen other states have enacted tax-limitation amendments.

The House is slated to vote on Barton's amendment on April 22.