A Fortune 100 financial services organization on Tuesday warned top lawmakers and Gov. Dannel P. Malloy that the revisions proposed to a state-run retirement program could end up costing individuals who participate in the plan.

Martin Noven, senior director of government markets for TIAA, wrote a letter to Malloy explaining that the changes the governor wants to make to the controversial legislation could reduce the amount of money an individual will be able to withdraw for their retirement by 28 percent.

Malloy said last week that he would veto the public retirement legislation if changes weren’t made to allow for more than one fund manager.

The bill Malloy threatened to veto would require every business with more than five employees that doesn’t offer a retirement savings plan to deduct three percent of an employee’s’ paycheck to deposit in a state retirement fund. Employers would not be required to contribute to the fund, but they would be required to offer the payroll deduction for the Roth IRA.

Opponents of the legislation argued that it will push those private-sector businesses selling competing products entirely out of the market. Malloy believes his proposed amendment to allow more fund managers to compete for the business will satisfy the concerns of opponents, but Noven disagrees.

Noven said the changes the governor wants to make to the plan have “proven to be unsuccessful and harmful to participants.”

If the ability to operate these funds is rotated among investment providers, “it is unlikely that any provider would accumulate a sufficient amount of assets to be able to offer low fees initially or reduce high fees over time,” Noven wrote.

Noven said that if the fees on these individual retirement accounts climb from 0.5 percent to 1.5 percent, an individual could see their retirement account shrink from $227,000 to $163,000.

“The 1 percent difference in fees and expenses would reduce the account balance at retirement by 28 percent,” Noven wrote.

Noven encouraged Malloy to sign the original legislation without seeking any amendments.

But lawmakers said as recently as Wednesday that language to add more than one fund manager will be in the budget implementation language.

“Governor Malloy is firmly committed to enhancing accessibility to retirement savings for all and believes the changes we have agreed to with legislative leaders will create the best system for Connecticut and lays the groundwork for a competitive marketplace,” Chris McClure, a spokesman for Malloy, said Wednesday. “We do not believe one company should have a monopoly.”