Rep. Gerry E. Connolly (D) joined federal employee unions on Wednesday to denounce a plan to target federal pensions to balance the budget, calling it an assault on civil servants and a tax on 2.2 million “middle-class” Americans.

“They are deliberately making the federal employee a scapegoat for the federal debt and deficit spending,” said Connolly, whose Northern Virginia district is home to about 120,000 federal workers and retirees.

The White House and congressional leaders are considering asking civil servants to contribute more to their retirement plans, to about 6 percent from the current 0.8 percent.The change, first reported Sunday by The Washington Post, was recommended by President Obama’s bipartisan fiscal commission and the non-profit group Third Way. It would amount to a 5 percent pay cut.

But Connolly and union leaders said in a conference call with reporters that the change would do more damage than cut the pay of federal workers. It would drive job-seekers from the federal government and hasten the retirement of hundreds of thousands of veterans who are eligible to leave, they said.

“People are going to look at that and wonder, is this really a career I want to choose?” Connolly said. “We’re making it a far less attractive choice for people entering the workforce.” About 60 percent of federal workers are eligible to retire, he said.

The growing support for higher pension contributions comes on the heels of a two-year pay freeze in place since January and a slowdown of hiring in many agencies. Many Republicans in Congress targeted civil servants as they campaigned last fall, saying they make more money than their private-sector counterparts. Many Democrats and union leaders dispute the claims.

The federal pension system became less generous in the 1980s, when the government required newly hired civil servants to pay into the Social Security system.

“It’s not the gold-plated system people are pointing it out to be,”said Maureen Gilman, legislative and political director for the National Treasury Employees Union. Other union officials speaking out against the pension plan Wednesday represented the American Federation of Government Employees and the National Association of Retired Federal Employees.