The UK's secret electronic intelligence agency GCHQ experienced "significant disruption" because of the floods last summer, a report has said.
GCHQ faced "significant disruption" in summer floods of 2007
Parliament's Intelligence and Security Committee said the Gloucestershire floods caused "severe problems".
GCHQ kept its most important operations going - but the committee said the disruption could have been more severe if the flooding had worsened.
Meanwhile, Margaret Beckett has taken over as chairman of the committee.
The former foreign secretary replaces Paul Murphy who joined the cabinet as Welsh secretary in the reshuffle following Peter Hain's resignation from the government.
The committee said in its annual report: "The summer floods in the Gloucestershire region caused significant disruption to GCHQ and its staff."
Staff and management at the agency were commended for their "tenacity and dedication" during the "difficult period".
The report says "business continuity arrangements" at MI5, MI6 and GCHQ will be reviewed.
Although GCHQ, which is based near Cheltenham, was near Walham electricity sub-station which nearly flooded, officials said operations would have continued using back-up generators.
The government responded to the report by saying GCHQ had identified what lessons were learned to try to improve the way it would deal with future crises.
The committee also said counter-terrorism work was adversely affecting other activities of the security services.
John Scarlett, the head of MI6, said the terror effort made up 56% of its work.
The committee said: "We are concerned that aspects of key intelligence and security work are suffering as a consequence of the focus on counter-terrorism priorities.
"We believe consideration may need to be given to separate additional funding to maintain the agencies' capabilities in these areas."
The committee urged a review of the DA-Notice system of advising the media on stories involving national security.
Dame Eliza Manningham-Buller, the former head of MI5, told the committee she had been "very, very angry" that an operation to arrest suspects in an alleged plot to kidnap and behead a British Muslim soldier was reported while it was ongoing.
"My officers and the police were jeopardised by them being on operations when the story broke," she said.
"The strategy of the police for interrogating those arrested was blown out of the water, and my staff felt pretty depressed about the fact that this had happened."