Observer Sport Monthly magazine is understood to have boosted the circulation of The Observer by as much as 11 per cent each time it has appeared with the Sunday broadsheet.
The monthly title is expected to significantly affect the forthcoming audited circulation figures for the paper – to be published by the Audit Bureau of Circulations this week.
The Observer’s average net circulation per issue for May was 408,748, down 0.13 per cent on April. But its average net circulation for the six months to May was 410,700 – up 1.37 per cent on the same period last year.
Observer Sport Monthly was launched in May and each issue has been supported by TV advertising. It also went on sale through WH Smith travel outlets from June.
An Observer spokeswoman says: “We are anticipating a really strong ABC for June. But it does not seem to be only Observer Sport Monthly that has influenced this, as we have been pushing the Sunday newspaper very strongly from a marketing point of view.”