By George P. Hassett

An alleged hooker asked an undercover Somerville vice cop repeatedly if he was a police officer before she took her clothes off and got arrested last week, police said.

Heather Robinson, 22, of 590 Shirley St., Winthrop, was arrested at the Holiday Inn on Washington Street and charged with sexual conduct for a fee March 12. Police said Robinson quoted an undercover officer $150 for an hour of sexual services after members of the vice unit identified a Web site displaying an advertisement offering prostitution in Somerville.

After Robinson accepted $150 for her sexual services and began to disrobe an arrest team entered the room and placed her under arrest.