Norton & Co, which handles PR for Lego's individual products, will not be affected by the review which will see five agencies vying for the lead business.
The major PR account, currently held by The Red Consultancy, is believed to be worth about £175,000. The winning agency will be in charge of brand strategy.
Lego PR manager Melissa Wallace said: "We are pitching our business, but we are completely closed to other agencies. We want a change in strategy next year."
According to PR Week, no decision is expected until the end of September at the earliest.
Red was brought in to promote Lego's educational benefits in September 2008.
A source at Red said it would not be working with Lego in 2010, owing to 'a change in PR strategy for the brand'. However, Red will be retained by Lego until the end of this year.