The publisher, which had considered options including splitting its regional and national newspaper businesses, said it would make cost savings of £20m after the sale of the titles.
The sale of The Racing Post will come as a surprise to many. It might only sell a little more than 71,000 copies, but it is seen as one of the group's flagship titles. It recently saw off competition from the failed Sportsman newspaper and is likely to excite attractive offers.
In all, 138 regional titles are being sold including, big papers such as the Birmingham Post, Birmingham Mail and Coventry Telegraph. Also being sold are South London Press, Reading Chronicle, Croydon Advertiser, Maidenhead Express and Surrey Mirror.
The sell-off comes after a four-month strategic review of the newspaper publisher's business conducted by investment bank NM Rothschild in which it said nothing would be ruled out.
However, radical changes to its business were dismissed by analysts over the last few days as has proved to be the case. In the case of splitting the national and regional titles, the company said that this option "would adversely impact shareholder value".
In the end, the publisher has said it will concentrate all of its efforts on the its national newspaper titles and key regional titles in Scotland, the North of England and Wales and UK and its digital assets.
Sly Bailey, group chief executive, said: "The proposed disposals will enable us to concentrate on the heart of the group and adopt a new, technology-led operating model that will ensure we serve our advertisers and readers better from a significantly lower cost base.
"The new integrated model will allow Trinity Mirror to develop as a multi-platform media business and capitalise on the enormous strengths we have in our core markets. Now this review has been completed we can move forward swiftly and turn our vision into a reality."
Racing Post is being sold off on the basis that it has little overlap in terms of readership, advertising base or editorial content with the group's other titles and operates as a standalone business within Trinity Mirror.
NM Rothschild is to advise on the disposal programme, which is expected to be completed during the second and third quarters of 2007, subject to offers.
The result of the review has also, Trinity Mirror said this morning, identified a number of areas to improve the performance of its businesses significantly by further investment in technology, which will see it integrate its print and online operations more closely.
The national titles are to get new-look websites designed to fully play to the strengths of the web, focusing on the key content strands of news, sport and showbiz.
The sites will be easier to navigate, featuring a substantial increase in multimedia and user-generated content in order to boost substantially unique users and online revenues during 2007.
Job cuts are also likely as it plans investment in IT systems that it says will transform the way it does business by "significantly reducing low value-added administrative tasks".
The businesses being sold reported sales and earnings before interest and tax of £132m and £27m respectively in the 26 weeks to July 2 2006.
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