A320
Air Traffic Control Fully Certified
Confusion; Situational Awareness
ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Air Traffic Control Separated Traffic
Airspace Structure; Human Factors; Procedure
Aircraft Y was a VFR pop-up off of ZZZ going southbound at 15;500 feet; requesting IFR pick up. Aircraft X was a ZZZ1 departure climbing from 14;000 feet to 23;000 feet. The ATCAA was active; which meant that instead of going up the jet route; Aircraft X was flying the airway. I had just signed in to my shift and was relieving the Radar Controller. It was apparent to me that the Controller being relieved expected Aircraft X to be flying up the jet route and was not expecting them to be on their current route. Once he realized that the two were traffic; he stopped Aircraft X at 16;000 feet. (they were in the climb out of 15;200 feet and about a minute away from being in conflict with Aircraft Y who at the time was still VFR at 15;500 feet. After stopping Aircraft X at 16;000 feet he then climbed Aircraft Y to 24;000 feet; making a loss of separation unavoidable. At this point I should have asserted myself and said 'no! Stop Aircraft Y and climb Aircraft X; you're going to have a deal.' I did not do this because I was not confident that I would get the point across and I didn't want to distract the radar Controller while he was working an extremely delicate situation. I also would have never expected a Controller to make the move that he did; and it caught me unaware. He then turned Aircraft X 60 degrees left. He never called traffic to either plane; but Aircraft Y keyed up and said they were staying at 15;500 feet; they saw traffic pretty close off their right side above them.At this point; the sector fell into such disarray that I terminated the relief briefing process and worked the Radar Assist for a few minutes to make all of the required point outs and coordination that I judged were not going to be done otherwise. The 60 degree turn on Aircraft X turned him directly into an [adjacent sector's] airspace. If Aircraft X had just kept climbing to 23;000 feet and Aircraft Y had waited 1.5 more minutes to get their off clearance and climb; positive separation would have been maintained the whole time.I suggest remedial training on order of priorities. A VFR pop up does not get first priority when there is an IFR aircraft in conflict with them. Also remedial training on separation minimums between VFR and IFR as opposed to IFR and IFR. Training on how to be assertive in unsafe situations and get the point across clearly that a plan needs to be changed. I wish that I had spoken up; and having the tool of knowing what to say would have made it easier to speak up. Also remedial training on what routes to expect when VIP movement shuts down normal routes.
Center Controller reported another Controller issued a climb to an aircraft that resulted in a loss of separation with another aircraft.