The mailing, sent to Express readers by Associated Newspapers, said that the Express was "no longer the great paper it once was" and asked if it was not time to change to the Daily Mail.
"Why not take this chance to join the thousands of other readers of our paper who are switching to the Daily Mail? But that's not all you get with the Mail. Every Saturday our free Weekend magazine has unrivalled TV listings with six large-format pages devoted to every day's programmes," the mailer read.
Express Newspapers disputed the advertisement's claim that thousands of readers had switched from the Express to the Daily Mail, and also challenged the ad for implying that the Daily Mail's TV listings were better than any other newspaper or magazine.
Despite evidence supplied by the Daily Mail in support of its claims on circulation, the Advertising Standards Authority judged that the evidence did not prove that thousands of readers of the Express were presently switching to the Daily Mail. It also found that the newspaper had not proven that its TV listings were better than all of its competitors, and asked Associated Newspapers not to repeat the claim.
However, another complaint about the ad, namely that it unfairly denigrated the Express, was rejected because the ASA deemed it to be an expression of the advertiser's opinion and concluded that it was acceptable.
It is the fourth time in 12 months that Associated has had complaints against it upheld by the ASA.
The two newspapers have been continually clashing in recent months fighting a phantom war, with each leaking details of planned newspaper launches and counter-launches to the press.
The Richard Desmond-owned Express was meant to be launching a London evening freesheet called the Evening Mail, but it has so far failed to materialise. The paper was meant to take on the Evening Standard and Metro, which are owned by Associated.
In response, Associated has floated the idea that it is launching a down-market tabloid to take on Desmond's Daily Star but, like the Evening Mail, there has been no material sign of it.
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