10 levels of the Rainbow Servant prestige class from page 54 of Complete Divine allows an arcane spellcaster full access to the Cleric spell list. They can learn and cast any spell from the Cleric spell list as if it was from the Arcane spellcasting class that allowed them entry into Rainbow Servant. Note that these spells still count as Divine spells for all purposes (most particularly Arcane Spell Failure.)
An important detail of the Rainbow Servant is that it gives full spellcasting progression. At first glance, it loses 4 spellcasting levels (from the table), but the text of the class doesn't mention this. Despite this almost certainly being an oversight, there is a rule that 'text trumps table', so the text overrides the table and you don't lose any spellcasting. Complete Divine has received both errata and reprints, and neither has changed the text or the table in question.