The Three Lions have continued to make the gesture before kick-off as a way to signal their opposition to racism and call for greater equality in society.
England stars took the knee in their first warm-up game against Austria a week ago, but a large section of supporters could be heard booing them.
That led to the squad calling a meeting to decide whether to carry, which they overwhelming voted to do, with boos heard again when they took the knee against Romania in their second warm-up.
The booing angered England boss Gareth Southgate, who has insisted his players will continue to take the knee during the tournament.
“The first thing is that collectively we are very disappointed that it happened. I think you have to put yourself in the shoes of a young England player about to represent his country,” he said.
“We’re all trying to move towards equality and support our own teammates because of some of the experiences they’ve been through in their lives, but people decided to boo.
“The most important thing for our players is for them to know we are totally united on it.
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“We’re totally committed to supporting each other, supporting the team, and we feel more than ever that we are determined to take the knee throughout this tournament.”
FA chief executive Mark Bullingham has also called for supporters to show those who take the knee more respect.
“We’ve been clear throughout, this is not a political gesture that the team are making,” he told the BBC.
“We’re not asking every fan to copy that gesture. We’re just asking them to respect it, and we do expect that they should respect it.
“They should get behind their team, cheer them on, and let’s have a brilliant Euros with the country getting behind the team.”
The UK Government have refused to join Southgate in condemning the fans who boo, with some Conservative MPs even stating they will refuse to support the team due to the players taking the knee.
But the Three Lions have now received a major boost from tournament organisers UEFA, who have reiterated their stance of zero tolerance of racism.
The governing body have also insisted that players should be free to take the knee to express their supporter for improved equality by making the gesture.
UEFA have also confirmed that a series of messages will be displayed during England’s first game against Croatia, calling for the players to be treated with respect.
“UEFA has a zero tolerance against racism and any player who wants to demand equality among human beings by taking the knee will be allowed to do so,” a UEFA spokesperson told the Daily Mail.
“We urge spectators to show respect for teams and players taking the knee.”