The Houston Chronicle is reporting that a presidential panel has concluded that: "The Obama administration rejected government scientists' requests to publicly detail its worst predictions about the oil gushing into the Gulf of Mexico and repeatedly underestimated the size of the spill."
You can finds copies of the four reports here. From Staff Working Paper No. 3:
The federal government's estimates of the amount of oil flowing into and later remaining in the Gulf of Mexico in the aftermath of the Macondo well explosion were the source of significant controversy, which undermined public confidence in the federal government's response to the spill. By initially underestimating the amount of oil flow and then, at the end of the summer, appearing to underestimate the amount of oil remaining in the Gulf, the federal government created the impression that it was either not fully competent to handle the spill or not fully candid with the American people about the scope of the problem. (Introductory remarks.)