The top Republican on the House taxing committee accused the Internal Revenue Service of putting Obamacare ahead of the millions of tax returns filed each year.

The IRS announced earlier this week that it would have to delay by as much as two weeks the start of the filing period for income tax returns. Officials blamed the 16-day government shutdown, saying the agency is now behind in its work.

The filing period may not begin until Feb. 4. The IRS processes 150 million tax returns every year.

Rep. Dave Camp, R-Mich., the chairman of the House Ways and Means Committee, faulted the new health care overhaul, not the shutdown, for sucking up time and resources from the IRS staff.

The delay would affect mostly those diligent, early filers who are used to getting a tax return check from the federal government in January.

"Given that the agency has already had nine full months, and still has nearly three more, there is no reason the IRS should not be able to do its job on time," Camp said.

While Camp claims the IRS has successfully avoided delays in the past, it's not the first time the IRS has been forced to move the start of the filing season. In fact, just this year, the IRS started accepting tax returns a week later than planned after a last-second fiscal cliff deal forced the agency to deal with a flurry of last-minute tax code changes.

Sarah Hall Ingram, the official in charge of implementing the Affordable Care Act for the IRS, told a House committee recently that while other aspects of the law are behind schedule, her agency was up to speed.

"I'm pleased to report that the systems and processes that the IRS has developed to support enrollment in the marketplace were launched on schedule and are working as planned," Ingram said in her testimony. "We have handled all requests received to date via the [Health and Human Services] data services hub, and turnaround times are meeting our goals."

Camp wants to know if IRS officials worked on the implementation of Obamacare during the federal government shutdown, when only essential personnel should have been working.

"While the IRS says it cannot start the filing season on time, somehow it found the most essential operation to be the implementation of the president’s health care law," Camp said. "The IRS needs to explain why implementing the president’s health care law is more important than processing tax returns in a timely manner."