A printing problem, described as "rare and complex", saw The Sun Sunday lose almost 700,000 sales this weekend.
The problem at the News UK printing press meant that many newsagents across the country did not receive copies of the paper until as late as 10am this Sunday, hitting morning sales.
The issue particularly affected vendors in more remote parts of the country, according to a News UK spokesperson.
News UK has written to advertisers promising a refund on the value of inserted offers and promotions in last Sunday’s edition of the paper.
The predicted loss of 695,000 represents a 36 per cent decrease on its average circulation in July of 1.927m and a 35 per cent decrease from the 1.95m sales predicted by News UK.
In the letter, News UK managing director Paul Hayes said: “On Saturday night, News UK suffered an extremely rare and complex technical problem which affected the printing and distribution of some of our newspapers. Expert staff managed to identify and rectify the issues overnight, and we managed to produce every edition of all our titles. Unfortunately, these measures delayed the distribution of The Sun on Sunday and anticipated UK circulation will be 35% below base. We had projected a sale of 1.95 million but as a result of these issues expect a sales loss of 695,000.
"I'm pleased to say that our systems proved robust and trouble free last night, but given the exceptional nature of this problem, News UK will rebate the value of insertions booked into both The Sun Sunday and Fabulous pro-rata for the weekend.
"We apologise for this error and have employed a series of contingencies to ensure that such events do not occur again.”
The printing problem also hit distribution of The Sunday Times but did not affect sales, according to News UK.
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