The outcome follows an eight-month Independent Office for Police Conduct (IOPC) investigation.
An independently chaired disciplinary panel found gross misconduct proven against Police Constable X and PC Russell Felgate at a hearing organised by the force on Friday, 16 July, and they were dismissed without notice.
They were both found to have breached the standards of professional behaviour for honesty and integrity; authority, respect and courtesy and duties and responsibility, a spokesman for the IOPC said.
Additionally, PC X was found to have breached the standards of equality and diversity, and discreditable conduct.
PC Felgate also breached confidentiality standards.
PC X cannot be identified owing to a direction made by the disciplinary panel, the spokesman said.
A third PC – PC Alice Price – received a written warning for misconduct after it was proven they breached the standards of professional behaviour in respect of duties and responsibility for failing to investigate the alleged domestic assault.
In September 2019, the IOPC began its independent investigation following a complaint referral from Sussex Police
The complaint related to an incident on 13 August 2019, when a woman called Sussex Police reporting she had been assaulted by her employer at an address in Chichester, West Sussex.
PC Felgate and another officer attended the incident and saw PC X was already at the address, the spokesman said.
PC X was off duty at the time but had been allegedly notified of the incident by the suspect, who was her personal friend.
PC Felgate and the other officer spoke with the alleged suspect and complainant but made no arrests and did not take any further action.
Nine days later, the woman contacted Sussex Police again, stating she had been under duress from PC X not to provide a statement and not to pursue the allegation of assault, according to the spokesman.
IOPC Regional Director Graham Beesley said: “PC X was a personal friend of the alleged suspect and was also known to the alleged victim.
“As such she was in a position of trust and abused that to exert improper influence over the complainant and attempted to interfere with the investigation being carried out by her colleagues.
“Without doubt this kind of police corruption erodes trust and confidence in the police and anyone who behaves in such a way can have no place in policing.”
As part of the investigation, the IOPC arrested and interviewed PC X on suspicion of perverting the course of justice and corruption in relation to the reported assault.
The IOPC considered evidence including her mobile phone records and that of the suspect.
The suspect for the alleged domestic assault was also investigated by the IOPC on suspicion of perverting the course of justice.
IOPC investigators also interviewed the other two officers, analysed their body worn video footage and obtained numerous witness statements.
Criminal charges against PC X and the suspect for the alleged domestic assault were considered and a file was referred to the Crown Prosecution Service (CPS).
The CPS decided not to bring any criminal charges against either of them.
Sussex Police agreed with us that the three officers had a case to answer for gross misconduct and arranged for the disciplinary proceedings to take place.
Detective Superintendent Rachel Carr, head of the force’s Professional Standards Department, said: “When members of the public call Sussex Police we expect our officers to respond and act in accordance with the force’s values, the Code of Ethics and the Standards of Professional Behaviour.
“On this occasion their actions fell short of that and they let a victim of crime down.
“This will not be tolerated and the force’s Professional Standards Department will act to address such conduct.”