Pharmaceutical giant AstraZeneca has been forced to reissue its financial guidance after a major blunder saw it email confidential forecasts to analysts last week.

The company emailed a Microsoft Excel spreadsheet to the analysts, on which it had failed to delete internal data that was intended to remain confidential. Its next official financial update is in three weeks' time.

AstraZeneca was notified by one analyst that the spreadsheet contained internal data, it is understood. The company then sent a message asking others to destroy its email instead of reading it.

The internal predictions left on the spreadsheet date from late last year, revealing better figures than it announced in December after writedowns on some drug experiments.

In a statement to the markets, AstraZeneca said it supported the official figures released in December, which included guidance for earnings per share at "the lower half of the range of $7.20 to $7.40".