The former Gunner has also revealed his frustration at the club turning their form round so late in the season, while suggesting investment is still needed at the Emirates
Until the club’s recent upturn in form, the French boss had been under increasing pressure at the Emirates with fans growing frustrated after a number of trophyless seasons and the Gunners’ woeful start to the current campaign.
Petit, who played under Wenger at Monaco before being signed by the north London club in 1997, has suggested that Arsenal would have regretted axing the 62-year-old.
"Sacking Wenger would have been the biggest mistake Arsenal could have made," said Petit at the Soccerex conference.
"He is the solution for Arsenal. He just needed to change a few things, then it would come back again.
"Arsene Wenger's contribution to the Premier League is huge. Football has changed so much in England, Arsene has been part of that.
"He is like the stone of Arsenal, if you kick him out you don't know where they will go.
"But I do hope Robin will stay. I would understand it if he left because players like him need titles on their CV.
"Arsenal have to pay the loans back but if you want to fight for titles, you need to find the right mix.
"That is why the criticism of Arsenal this season has been justified and they need to try everything they can to keep him."
However, despite his praise for his former boss, Petit has been left frustrated by the latest Arsenal resurgence, suggesting if they had found their form earlier in the season they could have been celebrating a much more successful year.
"Arsenal received huge criticism after the AC Milan disappointment," he continued.
"This affected the belief and ego of the players, which is why they came back with such a big hunger to show to everyone they were wrong.
"The performances since then have been magnificent.
"But I am disappointed as well. Why did they have to wait for the criticism to show people what they can do? I am quite frustrated because it proved they can do more."
The ex-Chelsea and Barcelona man has noted that despite Arsenal’s improved showings of late, there must be further investment at the Emirates during this summer’s transfer window.
"It always seems to be the same news. You believe Arsenal will sell their best players every year.
"I understand they don't want to be paying the same transfer fees as some clubs, it is nonsense to pay £40million for a player.
"But betting all your money on a young team? You need experienced players at some point in the season.
"Maybe this team have discovered themselves mentally now but you can't wait for outside help, you have to take your pen and write your own history."