Five's evening news bulletin has seen its ratings increase by 72% since Natasha Kaplinsky made her debut as presenter last month.
Kaplinsky was hired last year to replace Kirsty Young
Since it launched on 18 February, her 1700 GMT broadcast has attracted an average audience of 847,000 viewers.
Her second bulletin at 1900 GMT drew an average of 399,000 viewers - a 43% rise on the first six weeks of 2007.
Kaplinsky's first appearance attracted almost one million viewers - nearly double the usual teatime news audience.
AVERAGE EVENING NEWS AUDIENCES BY CHANNEL
BBC One (1800 GMT) - 3.6m
ITV1 (1830 GMT) - 3.2m
Channel 4 (1900 GMT) - 643,000
Five (1700 GMT) - 585,000
Source: Overnight viewing figures, 3-8 March, 2008
The channel's previous late afternoon bulletin went out at 1730 GMT.
Her second bulletin, two hours later, attracted 431,000 viewers - almost a third more than the average.
"We didn't expect this extraordinary jump in viewing figures," said Five's senior programme controller Chris Shaw.
The increase, he added, "fully vindicated our decision to bring her over from the BBC."