Gov. Deval Patrick on Tuesday pressed for an increase in the state's retirement age and a change to the way state pensions are calculated on Tuesday as he rolled out the next phase of pension reform he called necessary to ensure that the state's pension system remains affordable.

The governor's proposal would increase the minimum state retirement age for over 90 percent of state workers to 60, from 55, and require that employees work until at least the age of 67 to receive the maximum pension benefit, an increase from age 65. The legislation would also expand the timeframe used to calculate a retiree's pension to an average of the highest five years' salary as opposed to the current three-year average.

Patrick outlined his proposal at a State House press conference joined by House Speaker Robert DeLeo, Senate President Therese Murray and Treasurer-elect Steve Grossman as he highlighted a series of changes to the state pension system that would eliminate the potential for certain abuses and save the state an estimated $5 billion over the next 30 years, including $2 billion for cities and towns.

"A series of loopholes and avoided decisions has left us with an unfunded pension liability of $20 billion. That problem was not created overnight and it will not be solved overnight," Patrick said. "I support the defined benefit program but without these reforms it is not sustainable."

The bill also includes an anti-spiking clause limiting the annual increase in pensionable earnings to 7 percent, and eliminates the loophole exposed by the late-Sheriff James DiPaola that currently allows elected officials to collect both a salary and a pension if they had retired before seeking office. The legislation also allows retirement boards to require retirees convicted of a criminal offense related to their public position to repay benefits received since the date of the offense, not just the date of conviction. That provision could come into play this spring if former Speaker Salvatore DiMasi, who retired in January 2009 and now faces trial on public corruption charges, is convicted.