England coach Eddie Jones said an unexpected Italy tactic "wasn't rugby" as they frustrated the Six Nations champions before finally losing 36-15.
Italy led 10-5 at half-time as they chose not to compete at the breakdown, allowing them to step into the England line without going offside.
But the hosts found a way through with five tries in the second period.
"Well done Italy, very smart. We knew they'd come with something," Jones told BBC Radio 5 live.
"But it wasn't rugby. We haven't played a game of rugby yet.
"I'm not critical of Italy, they did what they needed to do to stay in the game."
Italy coach Conor O'Shea defended the tactic, saying: "Everything we did was completely legal; I was incredibly proud of what the players put out there."
At one stage, England captain Dylan Hartley and team-mate James Haskell asked referee Romain Poite to clarify the law, but the Frenchman replied: "I am a referee, not a coach."
Jones added: "Did we react quick enough? It's hard when you don't play rugby, it's like playing a different game out there.
"If your half-back can't pass the ball, the game becomes difficult. It's not the way you want to play the game. We wanted to move the ball and play some good rugby.
"We scored six tries and at the end of three rounds, if we were undefeated and with a bonus points, we'd be doing handstands. So we're doing handstands."
'Blue jumpers everywhere'
Italy played a novel tactic of not committing any men to the breakdown beyond the initial tackler, meaning no ruck was formed and any offside became irrelevant.
Italian defenders could therefore stand between England's half-backs, creating confusion for the men in white.
"How can you have players standing in your attack line? Even when there were rucks, there were people standing in our attack line.
"You look to pass the ball and there's a blue jumper there. You look in front and there's a blue jumper there. There's blue jumpers everywhere.
"He [Poite] had a terrible day. He wasn't refereeing rugby."
Asked if rugby's laws need to change following the game, Jones said: "I don't think anyone wants to see a game like that. No-one likes to see rugby not played in its proper form so World Rugby will have to have a very close look at it.
"I don't think there was anything good in that today. It didn't improve the game."
Italy 'ruined the match' - Dawson
The innovative tactics caused confusion among the spectators as well as those on the field, and former England scrum-half Matt Dawson laid the blame for a disjointed contest firmly with Italy.
The 2003 World Cup winner said on Twitter: "Well done Italy on ruining this international. Now World Rugby have to change the laws because of your inability to compete at this level."
O'Shea was not about to back down when Dawson's comment was put to him, saying: "I'd like him to sit down with World Rugby to look at some of the other games we've played this year, and if he's that good in the rules, actually make a comment after we were impacted as we were in the first game of this championship - but that's not for me to talk about now.
"We came here to have a go. If they want us to lose by 100 points, why should we? Why should we be normal? We should be ourselves. Rather than having a go, have a bit of humility and respect for guys who have very little in comparison to their counterparts.
"I was expecting this, if I'm honest."
'I'm sure Trevor Chappell would've been happy today'
Jones went on to compare the Italian tactic to a famous one-day international cricket match between Australia and New Zealand in 1981.
With one ball remaining, New Zealand needed a six to tie the match.
To ensure this couldn't happen, Australia's captain Greg Chappell ordered his brother Trevor to bowl the last ball underarm, a legal action at the time.
"Well, obviously they've been watching Trevor Chappell with the underarm bowl along the ground to make sure they couldn't hit a six," said Australian Jones.
"I'm sure Trevor Chappell would've been happy today."
Jones expecting 'proper rugby' from Scots
England have a two-week rest before they take on Scotland at Twickenham on Saturday, 11 March, and another victory would see them equal New Zealand's world record of 18 Test matches unbeaten.
"We've got Scotland in two weeks and they've got belief and confidence," said Jones. "We are looking forward to them coming down and I'm sure they're going to play proper rugby.
"This is our next test, and I'm sure [Scotland coach] Vern Cotter won't have those tactics. He's a New Zealander. They like the breakdown and the contest.
"I feel like I haven't coached today. Let's be serious. It wasn't rugby today."