Two police detectives have been disciplined after a 17-year-old boy was plied with cider before being questioned about a series of burglaries.

Sean Wall admitted involvement in the raids even though he could not possibly have committed some of them because he was in custody at the time.

The two detective constables faced a South Wales police gross misconduct hearing last week in respect of four potential breaches of professional behaviour.

Two were found to be proven. The panel decided that one officer should receive a final written warning and a written warning and the other officer two written warnings.

Both officers admitted Wall had consumed alcohol in their company.

Wall's solicitor, Nadeem Majid, told the Guardian the detectives collected Wall from Parc young offenders' institution in Bridgend, where he was being held awaiting sentence on other matters.

Majid said he was picked up at 9am, driven around Cardiff and given two bottles of "strong cider" as the officers pointed out locations where burglaries had been carried out.

They then took Wall to Cardiff Bay police station and allegedly encouraged him to confess to the raids, telling him that admitting the crimes would not increase his sentence when he appeared before a crown court judge.

Majid said he presumed the police wanted to boost its detection rate by getting Wall to admit to unsolved burglaries.

Wall was interviewed at about 7pm at Cardiff Bay that day, Majid said, and admitted to 11 burglaries.

Shortly before midnight Wall spoke to his solicitor and told him he had been given alcohol. Majid asked the custody sergeant to breathalyse Wall and he was found to be over the drink-drive limit.

Majid said that at the time Wall was interviewed – almost five hours before – he must have been "steaming". "It's frightening to think what his reading would have been at the time of the interview."

The solicitor said: "Getting my client to admit things he hadn't done in the hope it will improve crime figures takes policing back 25 years. It's likely in his condition he'd have agreed to anything. This goes as a warning that such behaviour will not be tolerated."

Wall's mother, Angela Rosier, said: "I think it is disgusting, how can they keep their jobs? They're definitely in the wrong career. Sean cannot believe how they are allowed to stay.

"I'm not leaving it like this, I am going to take this as far I can and am currently talking to my solicitor about further action."

The incident took place in 2010. The Independent Police Complaints Commission investigated the case and submitted its evidence to the Crown Prosecution Service because the officers had supplied drink to a 17-year-old. The CPS decided not to prosecute.

The IPCC's commissioner for Wales, Tom Davies, said: "These two officers dealing with Sean Wall have acted without integrity. It was right that they faced gross misconduct proceedings.

"When interviewing Sean the officers were obstructive in relation to his request for a solicitor. During one of the interviews in the police station Sean is heard on tape asking for a solicitor on no fewer than 17 occasions.

"The two police officers compounded this by providing alcohol to Sean even though he was below the age of 18. This was clearly not for any refreshment purpose and could be seen as a crude inducement for him to help clear up unsolved crimes.

"I am sure that members of the public will be as surprised as I am that police officers can purchase alcohol for somebody below the legal age and yet no offence was committed in law."

South Wales police assistant chief constable, Nick Croft, said: "These officers have acted in a manner which clearly falls well below the standards expected of them by the communities of South Wales. Their conduct will undoubtedly cause concern to members of the public, to the police service and their police colleagues."