A rape trial has been halted while claims a policeman had an affair with the alleged victim are investigated.
The Crown Prosecution Service (CPS) is examining other cases involving Det Con John Cragg, 42, who worked on a specialist sex crimes unit.
The officer, who is based in Blackpool, resigned on Thursday amid allegations he started an inappropriate relationship with the woman.
Lancashire Constabulary said it was co-operating with the CPS.
Mr Cragg gave no reason for leaving his job.
The proceedings against a man accused of attacking the woman, understood to be aged in her 30s, have now been put on hold at Preston Crown Court until the conclusion of the CPS inquiry.
A CPS spokeswoman said: "We asked for this trial to be adjourned and will be carrying out a further review of the case after the police investigation into the former officer's conduct has concluded.
"We are also reviewing all ongoing prosecutions that involve the former officer, but we will wait until after the investigation before taking any decisions."
A Lancashire Police spokesperson said: "We can confirm that on November 18 a detective constable working in Blackpool resigned from his post in the constabulary.
"He did not provide a reason for his resignation and an investigation is now under way.
"We continue to work closely with the CPS to review any implications of his resignation on cases awaiting trial."