A husband and wife nicknamed Fred and Rosemary West in their south Wales town have been jailed for grooming and raping teenage girls over three decades.

Peter Griffiths, 65, and Avril Griffiths, 61, repeatedly abused the girls at their home in Barry, in their van and during parties on a boat.

During the pair’s trial, claims were made that police officers were present when a girl was raped on a boat. South Wales police said it was investigating allegations of contact between officers and Peter Griffiths.

The couple were found guilty of rape, indecent assault and taking indecent photos of a child relating to three female victims between 1978 and 1993. Two further women have come forward to allege they were also attacked by the pair.

At Cardiff crown court on Thursday, Peter Griffiths was sentenced to 21 years in jail for eight counts of rape, three of indecent assault and two of taking an indecent photograph of a child. Avril Griffiths was sentenced to 15 years in jail for five counts of rape, two of taking an indecent photograph of a child and two of indecent assault.

The judge Jeremy Jenkins told the couple: “The offences were committed upon young, vulnerable and impressionable young girls. They were offered cigarettes and occasionally alcohol. I am quite satisfied you were systematically grooming those children. The two of you had few, if any, sexual boundaries. You engaged in group sex as a matter of course.”

The pair met when Avril was 13 or 14 and Peter in his late teens. By the age of 15 she was pregnant by him and she was taken into care. They married when she was 18.

When they were in their 20s they began “working as a team” to target girls, the court heard. Griffiths used his wife as “bait” to lure victims. She would give them cigarettes and alcohol and sometimes dress the victims in revealing clothing.

One victim claimed police officers were present when she was raped and that they were friends of Griffiths. She said Griffiths claimed to be a special constable, which South Wales Police later said was not the case. She told the court the officers would often brag about their jobs and say no one would believe her if she complained.

One victim, aged 13 at the time, was raped by the couple while Avril Griffiths held her down and told her: “Don’t worry, it’s not going to hurt.” The victim told the court that the couple were well known in Barry and were nicknamed Fred and Rose West.

In a statement read in court, one of the victims said: “I am still scared of them and I hate that, even though I am a mother in my 40s. I have flashbacks of what they did to me. It’s a recurring nightmare that I relive constantly.”

Wendy Brady, of the Crown Prosecution Service, said: “Peter and Avril Griffiths worked together befriending the girls before going on to sexually abuse them. They showed no regard for the welfare of the children they were abusing, treating them as objects to fulfil their sexual desires.

“The victims have shown great courage in telling the court what happened to them. We hope they can start to move forward knowing that Peter and Avril Griffiths have been brought to justice.”

DCI Justin Evans said: “Following the convictions of Peter and Avril Griffiths, two people have reported allegations of non-recent sexual offences to police. We are investigating these allegations and they are being supported by specially trained officers. Since the trial, further information concerning allegations of contact between police officers and the defendant Peter Griffiths have been reported to police. This investigation is ongoing.”