A300 Captain reported communications issues during take off with FADEC MEL that required the Engines to be in N1 Mode. The #1 Engine lagged significantly behind and a rejected take off was made. The flight crew returned to the Gate for Maintenance.

Narrative

The aircraft had five MELs prior to takeoff to include a FADEC issue that required the engines to be in the N1 Mode. The TRP (Takeoff Runway Performance) was considered inoperative and an auto-throttle off takeoff (non-profile) was briefed as per the MEL procedures. The Engine Pressure Ratio bugs were set to manual as reference only knowing the engines were in N1 mode for the entire flight. Upon taking the Runway for takeoff; I pushed the power up to 40% N1; selected TOGA and stated 'set thrust'. I initially pushed up the thrust but allowed the First Officer set takeoff thrust; as briefed. As we began to well into our acceleration; I noticed that the First Officer did not call 'thrust set' as well as no '80 kts.' call. This prompted me to look at his throttle adjustment for takeoff and I observed him closely looking at the engine instruments and pushing up the #1 throttle stating '#1 doesn't look right'. I quickly looked at the throttles and pushed the #1 engine forward further and did not notice; what should have been a power increase and the First Officer stated '#1 is lagging'. My view of the engine instruments was at a glance; at best; knowing we were accelerating and I was the pilot flying maintaining aircraft control on the Runway. What I did observe initially was the noticeable split in Engine Pressure Ratios because that was at the top of the engine instruments and I did not observe a noticeable movement in any of the other instruments (N1; EGT; etc) nor feel any engine acceleration due to the throttle being pushed forward. To note; all of the above happened in a matter of seconds. Without further delay; I rejected the aircraft around 110 kts. as there was doubt as well as little confidence that the #1 engine was at takeoff thrust due to First Officer verbal cues along with his adjustment of pushing up #1 throttle beyond where the #2 throttle was set (split throttles). For safety of flight and my concern for the aircraft's ability to get airborne with two engines running at the correct thrust a Rotation was accomplished uneventfully. We then discussed with ZZZ and ZZZ1 a plan to return to the Gate. Also to note; on debrief of the event I queried the First Officer as to what he was referring to when he was adjusting the #1 throttle along with the statements '#1 doesn't look right' and '#1 was lagging' and stated he initially did see the Engine Pressure Ratio split but referenced the N1; N2; EGT; etc for the throttle discrepancy and lack of response. Because there was no confidence in takeoff thrust being set properly on the #1 engine along with a lack of callouts assuring takeoff thrust was correct for the #1 engine by the First Officer by making the statements '#1 doesn't look right' and '#1 is lagging' a decision was made to make a rejected takeoff. With a doubt in safety of flight; the Rotation was accomplished uneventfully. With the statements by the First Officer and the lack confidence in the takeoff thrust being set for the #1 engine; I don't think there is a prevention. The only option with those factors as stated above; with a doubt in the aircraft's thrust setting; would lead to a rejected Takeoff.