DENVER – Republicans in the Colorado Legislature are asking Democratic leaders to oppose a ballot proposal to raise taxes by $3 billion over five years to help fund the state’s education system.

Every Republican in the House and Senate signed on to a letter sent Tuesday to Gov. John Hickenlooper, Senate President Brandon Shaffer, and House Democratic Leader Sal Pace. The letter urges Democrats to oppose the initiative on November’s ballot. It seeks to raise the sales and use tax rate to 3 percent, up from 2.9 percent, and raise the state’s individual and corporate tax rates to 5 percent, up from 4.63 percent.

The increases would be in effect from 2012 to 2017.

Hickenlooper has said he is not planning to oppose or endorse the proposal.