Gill said the Glazers were not interested in selling up and are running the club in the right way.
Related ArticlesMichael Johnson arrested over alleged headbutt on United fanFive reasons why the Red Knights will failWayne Rooney goalsRed Knights to target debt in bid for UnitedSmalling up for U-21 adventureProfile: 'Red Knight' Jim O'NeillHe said at the Soccerex conference in Manchester: "The owners are very long-term owners and have shown that with Tampa Bay which they took over in 1994-5.
"They are not sellers, that's not saying people like these Red Knights can't come forward with some ideas.
"But there is no indication to mean that they want to sell and in that case they cannot buy the asset, it's not for sale.
"The Glazers have no wish to sell and from our perspective they are running the club in the right way."
Gill questioned how a Red Knights' takeover would work at United.
He added: "The Red Knights proposal, the idea of having 20, 30 or 40 very wealthy people running Manchester United, I don't know how it would work in practice.
"The better-run clubs are where there is clear single decision-making and it's quick and efficient - Roman Abramovich at Chelsea, Sheikh Mansour at Manchester City, Silvio Berlusconi at AC Milan.
"Having a number of wealthy people involved - they will all want to be involved in decision-making.
"I'm not sure what their endgame is but the endgame is irrelevant.
"The vast majority of fans of Manchester United should be happy with what we are doing and staying at the top of domestic and world football."
Gill said there were bound to be dissenters among United's large fanbase but that manager Sir Alex Ferguson was very comfortable with the ownership situation.
He added: "We have 330million followers around the world, that's a key strength and within that it's highly likely you will have some dissenters and some people who are not happy with what's going on and would like to change it.
He also insisted the £80million transfer fee from the sale of Cristiano Ronaldo was still available for Ferguson to spend on top players.
"Without doubt," he said. "We are looking at players all the time, the money from Ronaldo is sitting there in the bank account, we have been clear on that.
"But Alex has been very clear he is not going out to chase and overpay for a player just because everyone else thinks we should. He's a Scot, he wants value for money.
"We have spent a lot of money on Chris Smalling [from Fulham] and that's the sort of player we want to bring in - a young player who we feel will develop as a player and hopefully give us service for many many years to come."
Gill accepted some of those involved in Red Knights were credible but was scathing about merchant banker Keith Harris, the former Football League chairman who has been involved in a number of takeover bids of top-flight clubs and who had called on fans to boycott United matches.
He said: "We are aware of Jim O'Neill [Goldman Sachs economic adviser] in that he was on our board before the takeover, Mark Rawlinson was our adviser at Freshfields [law firm].
"Keith Harris will go anywhere there is publicity around, we know that and we accept that, that's his modus operandi but if you looks at his track record in football I don't think it's anything to write home about.
"These are credible people and have every right to do what they think is in the interest of the club.
"But that's not going to take them anywhere if the Glazers don't want to sell, and they have no wish to sell and from our perspective they are running the club in the right way."
He also defended the Glazers' lack of attendance at United matches and insisted the debts - £507million in bonds with the Glazers' personal PIK debts around £202million - are serviceable.
Gill said: "They don't come to many games but they are very passionate about the club, they do understand what's required to run a successful sports team, that you have to invest in the product, on the pitch, in the training ground and in the stadium, they watch every match on TV and I think they have been supportive.
"You have many examples of owners who come in and try to pick the team, be very visible, and they have taken the view they are not there to do that.
"I don't think their lack of attendance should be interpreted as that they are not passionate about the club."
Gill said the clubs' debts were easily covered by the income.
He added: "We have an element of the debt that is very easily serviced by the cashflows of Manchester United, we are in a sport that is getting bigger all the time and as one of the leading clubs we should benefit from that growth.
"We believe we have a much more appropriate and flexible financial structure in place.
"In an ideal world people would like to not have a mortgage on their house but that doesn't mean they don't enjoy the benefits of living in that house and can't afford that house."