Highly hydrophilic non-nucleosidic tags with multiple labels are provided for use in nucleic acid probes. The tags are branched structures having a phosphodiester backbone, which have the advantages of a small dimensional size and high hydrophilicity. After the tag is labeled, its high negative charge and minimal size help to keep the carriers away from DNA or RNA molecules, due to repulsion between negative charges. Non-specific intercalation and steric hindrance are therefore minimized, and the hydrophobicity, if any of reporter molecules is reduced. The probes are used in place of conventionally labeled oligonucleotides for a variety of hybridization reactions.