The consultation examined expansion at Heathrow airport, including the construction of a third runway and changes to the use of the existing facilities.
Kelly said, "Almost 70,000 individuals and organisations representing all sides of the debate responded to the Adding Capacity at Heathrow Airport consultation, which my officials are still analysing. That process is itself also subject to quality assurance and peer review to ensure its integrity.
"Our work on analysing the consultation responses, on completing the Equalities Impact Assessment, and finalising the overall Impact Assessment will take some more time to complete. But I intend to inform the House of my decision on the future development of Heathrow airport before the end of the year."
Commenting on Ruth Kelly's announcement, Liberal Democrat shadow transport secretary Norman Baker said:
"Today's delay could be a chink of light for those fighting against Heathrow's expansion.
"It looks like the Government has realised quite how unpopular its policy is and is now looking for a way out.
"Alternatively it could be that BAA is away on holiday and Ruth Kelly is simply awaiting further instructions from the aviation industry," he said.
Kelly added that, "the Government supports the further development of Heathrow by adding a third runway and exploring the scope for making greater use of the existing runways, subject to meeting strict local conditions on air quality and noise and improving public transport access."