Newcastle Crown Court heard that Welsh transported Nessar Ali to deals as well as answering his phone on his behalf.
Prosecutor Michael Bunch told the court that the officers' "repeated requests" to be supplied with drugs were met from February.
He said: "The supply to the undercover officers on all but one occasion involved a man called Nessar Ali.
"This defendant's first involvement appeared to be on the 23rd of March when his vehicle was seen by these officers to transport Ali to the scene of the exchange."
The court heard that just over a month later, Welsh supplied cocaine to the officers with a purity of 98%, before doing so again in the August.
Mr Bunch added: "That appeared to be this defendant coming into the picture more clearly and the evidence shows throughout the time period he's involved in some communication between others.
"He drove Ali on a number of occasions and took him to supplies on other occasions."
The prosecution claimed that Welsh had also been in telephone contact with co-defendant Aaron Momat five times on one day about deals.
The court also heard that in the July, Welsh travelled to Spain with his partner and took his mobile phone with him which was traced to the supplying.
Welsh, now 26, of Harbour View in South Shields, pleaded guilty to being concerned in the supply of a class A drug.
Gavin Doig, defending, mentioned a number of letters submitted to the court displaying positive character references.
Mr Doig accepted Welsh had played a role but said: "Even when he was at his most involved, this is someone who is not fully committed or invested in the operation.
"That perhaps gives hope in the future that he won't make a similar mistake and fall into error again."
Mr Doig also told the court that Welsh hadn't been able to see his young child or partner due to long waiting lists for people visiting custody.
Judge Amanda Rippon told Welsh: "You fall to be sentenced for your involvement in that supply in that operation.
"There are factors that put you in a significant role but there are also factors of lesser role.
"You were of previous good character prior to this offending.
"You had an important job with your father's business, a job which you are not going to, as I understand, return because there is only one sentence in this case as you know."
The judge sentenced Welsh to three years and four months in total behind bars.
She accepted custody would have an effect on his immediate family but added that drug dealing "wreaks havoc on lives."
Last month, Ali, 23, of Wallington Grove,, South Shields, was jailed for five years.
Momart, of Alice Street, South Shields, was sentenced to three-and-a-half years.
Meanwhile Christopher Scurfield, 42, of Rowland Street in Washington, was given five years for his role in supplying cocaine.