The holiday company is looking to build a shortlist ahead of a pitch in April.
The winning agency will overhaul its online activity for 2008 based on a digital brief that includes strategy, tactical advertising, web design and technical elements.
Butlins' digital media planning and buying account has been held by Profero since 2005. Digital creative is handled by Design UK.
Beechwood handles Butlins' above-the-line duties.
A spokeswoman for Butlins said the company had no plans to change its existing advertising relationships.