In his first public statement on the campaign to oust the Glazer family, Gill said there was no chance of them bowing to pressure from a group of wealthy supporters known as the Red Knights who are planning to raise more than 1 billion pounds to buy England's most globally popular team.
Speaking at the final session of the Soccerex conference in Manchester, Gill said the growing fervour to take over from the Glazers, who bought the club against a wave of opposition from fans who feared they were loading it up with too much debt, would be strongly resisted.
"The owners are long-term owners," said Gill. "They have shown this with their ownership of the Tampa Bay Buccaneers. They are not sellers."
Launching a strong defence of the increasingly under-fire Glazers, Gill continued: "They may not come to many games but they are passionate about the club. They understand sport and what is required to run a successful sports team.
"There are many examples of owners who have tried to come in and run clubs, to pick the team and be very visible. They are not there to do that.
"They have a fantastic manager in Alex Ferguson and they realise that in order to get the most out of the asset, they need to leave those people there. Their lack of attendance at games should not be interpreted that they are not passionate."
More than 20,000 Manchester United fans have joined the campaign to force the Glazers out in the last 24 hours. Manchester United Supporters' Trust (MUST) are backing a move by the Red Knights but Gill repeated they were wasting their time.
"People like these Red Knights may come and put a plan to the owners but unless the owners want to sell - and they have given no notification that this is the case - then the asset is not for sale."
BOND ISSUE
The Glazers launched a bond issue last month to raise 500 million pounds in a bid to re-align their debts. Gill, who refused to take questions from the floor, said the debts, reported to be about 716 million pounds, were easily sustainable and were not a cause for panic.
"Yes we have element of debt but football is getting bigger all the time," he said. "We've replaced bank debts with a seven-year bond repayable in 2017. We have fixed the interest payments at 45 million pounds per year. We have to be very pleased with that. We think we have a much more appropriate financial structure in place."
Speaking of opponents, he said: "They have every right to do what they think is in the interest of the club but it will not take them anywhere.
"From our perspective the owners are running the club in the right way. If I look at the Red Knights' proposal, the idea of having 20, 30, 40 people owning and running Manchester United, I just don't know how it would work. The better owned clubs are ones with clear, single, efficient decision making."
Earlier, Duncan Drasdo, MUST chief executive said that after the Red Knights' plans were made public a day earlier, there had been an "incredible uptake" in support of the campaign.
"A month ago, prior to the publication of the bond prospectus,
