This is United's worst start to the season since the first edition of the Premier League in 1992
United have lost both of their opening games and currently sit bottom of the Premier League.
Manager Erik ten Hag cancelled the players' day off on Sunday following their woeful 4-0 defeat by Brentford on Saturday.
The statement from Must said: "This really does feel like rock bottom."
The supporters' trust added: "The ultimate responsibility for the terrible state of our football club must lie with its owners, the Glazer family.
"It is now for them and their management team to explain to United fans just why we are in this state, and what they are going to do about it.
"We will be raising fan concerns directly with the club and demanding answers for supporters on issues including ownership, debt, dividends and team performance and the need for real change on all these fronts."
The supporters' group, who are one of the largest in the world with over 200,000 members, said "unity really is paramount above all else" and "one united voice directed to the club and owners is needed more than ever".
Ten Hag has become the first manager since John Chapman in 1921 to lose his opening two games in charge of the club.
Former Norwich forward Chris Sutton told BBC Radio 5 Live's Monday Night Club that it has taken Ten Hag two games to realise "the magnitude of the situation".
"I don't think it can get any worse - they have hit rock bottom. The club needs to lower the expectation, if you look at the last decade they have never really challenged," he said.
"They have been miles off for the best part of a decade - if you look at the recruitment over that time can you name one player that has been a massive success that United have brought in? The recruitment has been awful."
Following their 2-1 defeat by Brighton on the opening weekend of the season, United have been linked with various transfer targets, including Bologna striker Marko Arnautovic and 27-year-old France midfielder Adrien Rabiot.
The former was the subject of a widespread backlash and was described as a "PR disaster", while the latter is thought to be an underwhelming response to the ongoing problems at United.
The loss to Brentford further exposed the cracks in Ten Hag's squad and former United defender Gary Neville said on Sky Sports the recruitment has been "a horror story".
"It has become a graveyard for players, where players are even considering not coming in," he said.
"He [Ten Hag] is obviously a fantastic coach but he has been dealt a really bad hand. To not get the players he wanted in is an absolute shocker."
Another battle Ten Hag must contend with is the ongoing saga of whether Cristiano Ronaldo will leave the club before the transfer window closes, with reports once again emerging that he is unhappy.
"There is a massive decision to make on Ronaldo," Neville said. "He is obviously not happy, the problem is if they lose him there is nothing left in the goalscoring part of the pitch. I genuinely think if he leaves and they don't bring people in they could finish bottom half of the table."
To add fuel to the fire, United face their toughest challenge yet when they host Liverpool on Monday, 22 August.
-- Courtesy of BBC Sport