(CNN) -- President Obama on Wednesday called for a reform of the much-maligned federal earmarking process.
President Obama says future earmarks should be made public on lawmakers' Web sites.
Earmarks are unrelated pet projects that members of Congress insert in spending bills.
The president maintained that earmarks can serve a useful purpose, but he said it is time for Congress and the White House to embrace a new set of guiding principles.
His remarks came the day after the Senate passed a $410 billion spending bill that included nearly 9,000 earmarks, which are projects designed to benefit individual legislators' districts.
The earmarks in the spending bill are worth nearly $8 billion. Many critics have deemed them as wasteful, and some observers have questioned Obama's pledge to end such spending.
Some lawmakers urged Obama to veto the bill -- saying it goes against the president's campaign pledge. Watch what's in the spending bill »
Obama said that while he would sign the bill, which funds the government for the remainder of the current fiscal year, future earmarks should "have a legitimate and worthy public purpose." CNNMoney: The truth about earmarks
Earmarks sought by members of Congress, he said in an appearance at the White House, should be aired on those lawmakers' Web sites in advance "so the public and the press can examine them and judge their merit for themselves."
Each earmark, he added, also should "be open to scrutiny at public hearings, where members will have to justify their expense to the taxpayer."
The president also said that any earmark benefiting a for-profit private company "should be subject to the same competitive bidding requirements as other federal contracts."
"The awarding of earmarks to private companies is the single most corrupting element of this practice," he said.
"Private companies differ from the public entities that Americans rely on every day -- schools, police stations, fire departments -- and if they are seeking taxpayer dollars, then they should be evaluated with a higher level of scrutiny."
Obama added that earmarks should "never, ever be traded for political favors."
The president pledged to seek to eliminate any future earmark that has "no legitimate public purpose."
Obama has broken with many of his more conservative critics in opposing an elimination of the earmarking process.
If done right, he argued Wednesday, earmarks "give legislators the opportunity to direct federal money to worthy projects that benefit people in their district, and that's why I have opposed their outright elimination."
He conceded, however, that some earmarks "have been used as a vehicle for waste, fraud and abuse. Projects have been inserted at the eleventh hour, without review, and sometimes without merit, in order to satisfy the political or personal agendas of a given legislator, rather than the public interest."
Sen. John McCain, R-Arizona, called Obama's earmark announcement an "opportunity missed."
"The president's rhetoric is impressive, but his statement affirms we will continue to do business as usual in Washington regarding earmarks in appropriations legislation," McCain said in a statement. "The president could have resolved this issue in one statement -- no more unauthorized pork barrel projects -- and pledged to use his veto pen to stop them."
White House officials have tried to dismiss the current spending bill legislation as "last year's business" that Obama is dealing with reluctantly.
Top Democrats, including House Majority Leader Steny Hoyer of Maryland, have suggested lawmakers do not appreciate being dictated to on an issue that is a congressional prerogative.
Asked last week about the administration's plan to put forth guidelines to overhaul earmarks, Hoyer said flatly, "I don't think the White House has the ability to tell us what to do."
He paused and quipped to reporters, "I hope you all got that down."
Obama's budget director made a vow Sunday that the president will bring a halt to pork-laden bills.
"[Such bills] will not happen when the president has the full legislative and appropriations process in place," Peter Orszag, director of the White House Office of Management and Budget, told CNN's "State of the Union With John King."
He argued that the White House had little choice but to support the omnibus spending bill, which it inherited from the previous administration.
"This is like your relief pitcher coming into the ninth inning and wanting to redo the whole game," Orszag said. "Next year we're going to be the starting pitcher, and the game's going to be completely different."
But House Minority Whip Eric Cantor, R-Virginia, rejected this argument and said that Obama had vowed to take action against earmarks during the presidential campaign.
"If you make a promise, people expect that you live up to it. And that's why this administration's refusal to go in and change this bill, I think, is a false position," Cantor told "State of the Union."
"There is no way anyone could take what Mr. Orszag has said with any credibility."
House Minority Leader John Boehner, R-Ohio, said Tuesday that Obama can't just say the bill is last year's business. "I've asked the president to veto this bill," he said.
"Listen, this is a new Congress, and this is a new president."
CNN's Ed Henry contributed to this report.