A number of leading media agencies, believed to include Carat and Starcom, have pulled significant amounts of money out of The Times in the past week.
And ad industry body ISBA has issued guidance for advertisers and warned them to "keep close to their media agencies".
ISBA's director of media and advertising, Bob Wootton, issued a statement to members that read: "Media Week has reported that The Times announced to agencies last Wednesday that it will be reformatting its editorial to five columns, and its advertising grid from six columns to seven.
"This announcement is not accompanied by any significant upward change in The Times' circulation or readership.
"Any such changes in the number of columns has potential impacts on the cost of advertising space, as fractions of whole pages are typically priced per column. A move from six columns to seven could therefore in theory signal a price rise of 17%.
"The purpose of this note is to alert ISBA members to this development, and remind them that the price of advertising time or space should always be considered in the context of the volume and profile of a medium's audience delivery, neither of which have changed materially in this case.
"We therefore encourage members to keep close to their media buying agencies to ensure that there is no unnecessary or unwarranted inflationary impact on any of their media plans that are affected by this announcement."
The Times declined to comment, but in a letter published in this issue of Media Week, trading director Dominic Carter said: "In every conversation that we have had with the agencies, I would compliment the maturity with which they have dealt with the column changes on behalf of their clients. Far be it from me to say that it does not present them with a challenge but, in this instance, rage is not an emotion that plays a part in any conversation that we are having. . .
"We take care to ensure that our customers are made aware of any changes in our business when we can, but as most will appreciate, this is a competitive market and there are times when this is just not possible."
Times format change sparks agency alert
LONDON - The Times has suffered an industry backlash following Media Week's revelation that it could hike the cost of ad space by up to 17%, with at least two media agencies pulling spend from the paper and ISBA issuing a stark warning to advertisers to reject unjustified cost increases.