The maker of one of the country’s most popular diaries has pledged that it will never again use Hitler’s birthday as an “interesting fact of the day”.

The April 20 entry in the Collins Debden 2009 diary was spotted by central London art gallery owner Helly Nahmad. But his initial complaint to the company went unanswered so this week he wrote again. The second time the company responded and has now said that the reference was not in next year’s diary and would not appear again.

Mr Nahmad said: “There is a fact for every day in the diary and for April 20 it said Hitler’s birthday. At first I thought I would scribble it out because I didn’t want to look at it. But then I thought it was so wrong and insensitive.

“This is not just a Jewish issue because it would be offensive to many other people as well.”

Mr Nahmad said he had not noticed any other controversial names.

Peter Cottrill, marketing manager for the Glasgow-based publisher, said: “We purchased in good faith four sets of editorial information which contained significant events that happened on individual days. We gave a brief of what we were looking for and it was not anything like this. Nothing like that has appeared before and will never appear again. Our editorial department is conducting a review.

“On behalf of Collins, I would like to apologise that this entry appeared in the first place and that any offence was caused by it.” He said that the diary note would not, in any case, have been included in the 2010 diaries.