The Manchester United Supporters' Trust has issued a statement in the wake of Jose Mourinho's comments about the Old Trafford atmosphere.
Mourinho said the stadium was "quiet" as United beat Huddersfield 2-0 on Saturday, going on to cite Portsmouth's Fratton Park as an example of a good atmosphere.
In a statement, MUST said: "We note our manager's further comments regarding the poor atmosphere within Old Trafford following the Huddersfield home game.
"The decline in atmosphere is by no means limited to Old Trafford. It's an issue affecting clubs throughout the country. And it's certainly not an issue specific to Manchester United supporters -- our away support is widely acknowledged, by fair minded fans, as the best in the country."
Speaking on Saturday, Mourinho was asked about new signing Alexis Sanchez before branching off to discuss the crowd.
"He played only three [matches since joining from Arsenal] and the first at Old Trafford, and I think Old Trafford, in spite of being a quiet stadium, the pitch is big, the grass is nice and obviously the players feel very comfortable playing here," he said.
When then asked to explain his comments, Mourinho replied: "It's not Portsmouth.
"I remember Portsmouth -- such a small stadium, the atmosphere was absolutely incredible. In here, the atmosphere is a bit quiet and there is not very [much enthusiasm]. But the players like to play at home."
Earlier this season, Mourinho said United supporters were "very quiet" during the 2-0 win over Leicester in August.
He also, after the 1-0 win over Tottenham in October, expressed his unhappiness with United fans over what he regarded as unfair treatment of Lukaku.
MUST added that a breakdown in the relationship between the fans and the club's owners may be part of the problem.
"We believe that atmosphere is primarily dependent on the perceived relationship between fans and club -- including the degree of supporter ownership and engagement," the group added.
"In the absence of any imminent changes in the former we therefore concentrate on other areas where we can have an impact in the short to medium term."