Last year, circulation slipped to 17,422.
Overall circulation slipped 5.7percentto to 2.07 million.
Its sister paper, the Ipswich-based East Anglian Daily Times, saw circulation slip slightly by 0.5% period on period to 29,7729
The Economist's global circulation slipped back in 2012 but it still sold nearly 1.5 million copies around the world.
But as newspaper circulation slipped, The Post-Intelligencer lost ground much faster than its rival; its weekday circulation averaged about 118,000 in 2008, down from 196,000 a decade earlier.
The newspaper, published by the Tribune Company, said it also would pay rebates if its circulation slipped below a guaranteed minimum, according to a letter delivered to advertisers.
But its combined print and digital average weekday circulation slipped 11% year-on-year to 516,165 during the six-month period between October and March, according to data released last week by the Alliance for Audited Media AAMM).
The Sun's red-top rivals, the Daily Mirror and the Daily Star - which continues to publish pictures of topless women - did not appear to benefit from the Sun's circulation slip.
An indication of the general malaise in the regional market is shown by the Evening Post's circulation slip of 10.9% year on year in the six months to last December, to 34,851.
Her editorship of the two papers will be remembered for the high-profile campaigns she instigated around issues such as paedophilia and the introduction of "Sarah's law", the Help for Heroes campaign for members of the armed forces, and the case of Baby P. But she was unable to halt the sales decline at the Sun, which saw its circulation slip to below 3m again this year.
