Tottenham's majority owner is "wholly committed" and ready to produce the investment required to "rebuild" the club.
Spurs narrowly avoided a first relegation since 1977 on Sunday after an emotionally-charged fanbase inspired Roberto De Zerbi's team to a 1-0 home win over Everton.
Tottenham finished 17th, two points above West Ham, but it has been a disastrous Premier League campaign, with De Zerbi the third head coach of the season.
After Daniel Levy was invited to step down as chairman in September following a 24-year tenure, majority owner ENIC -- run by the Lewis family -- has frequently faced criticism.
Chief executive Vinai Venkatesham and sporting director Johan Lange have also felt the brunt of fan anger and on Monday the Tottenham Hotspur Supporters' Trust urged this season to be viewed as a "very serious warning" to the board.
In an open letter to fans, non-executive chairman Peter Charrington said: "Last September, we recognised that something seismic had to change at Spurs. The Lewis family stepped in and authorised a full reset.
"That decision was not taken lightly, and it came later than it should have. But what has been put in motion is real, and it marks a genuine break from what had come before.
"As part of that process, we discovered some uncomfortable truths... football success had not been driving our decisions.
"Two 17th place finishes in a row is not acceptable, and we will not dress it up as anything other than falling well short of what this club expects.
"Since September, we have restructured leadership across the club, with a refreshed executive and football structure. Most of this team are already in post and others will arrive in the coming weeks.
"The board are committed to this leadership group and will give them the stability and support they need to run this club in the right way.
"Roberto De Zerbi is signed as men's head coach for five years, a reflection of our belief in his ability and our commitment to build back to where we need to be.
"He is passionate, committed and positive in everything he does, and represents the kind of football and ambition that Tottenham Hotspur should stand for.
"The Lewis family are wholly committed to this club and to this rebuild. They will provide the stability and investment needed at every level to move us forward, and they see that as a long-term responsibility, not a short-term fix.
"This season fell well short of what Tottenham Hotspur demands. We must be in the fight with the best teams in this league, every season, and we are rebuilding this Club with that standard in mind.
"We will get back to where we belong."
Tottenham Hotspur Supporters' Trust called for "a moment of reckoning" after the ninth-richest club in world football almost dropped into the Championship.
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"This season must be viewed as a very serious warning," a statement read.
"Finishing where we have is not the outcome of one bad result or one difficult season alone. It is the consequence of repeated failures, poor decisions, and a lack of leadership over a sustained period.
"There must now be a moment of reckoning for the club. Honest reflection, accountability, and meaningful change are required if the club is to recover and rebuild."