The advertising watchdog received complaints about two television advertisements, one focusing on the Ashes and the other on the British Lions tour of South Africa.
The ASA says it was misleading to state in the ads that viewers could see “every moment” in high definition because installation wait times meant this was unlikely to be the case.
Sky says it amended on-screen text after 6 June to warn that installation may happen “after the Ashes has started” when it realised there was a chance the process might not complete before the start of the series.
The watchdog says existing customers registering from mid-April were unlikely to have a Sky+ HD service installed in time to watch either tournament in full because a 12-week waiting period meant no installation until mid-July.
The Lions tournament ran between June and July, while the Ashes took place between 8 July to 24 August.
A press ad was banned on the same grounds.