Premier Daniel Andrews also confirmed the death of two men in their 90s, bringing the state's death toll from the virus to 44 and the national toll to 128.
The men were residents of aged care facilities.
Of the state's new cases, 97 are connected to known and contained outbreaks while 387 remain under investigation.
The premier said new data has found nearly nine in 10 people, some 3400, did not isolate between feeling sick and being tested from July 17 to 21.
"They have gone out shopping. They have gone to work. They have been at the height of their infectivity, and they have just continued on as usual," Mr Andrews said.
About 53 percent of people also did not isolate between when they had their test taken and when they received the results of that test.
"We certainly cannot have one in two people who are waiting for a test result simply going about their business as if they didn't have symptoms, as if they weren't waiting for a test result, as if this wasn't a global pandemic," he said.
The state's previous record was 428 cases on Friday, although daily case numbers have consistently been in triple-digits for three weeks.
Victoria is coming to the end of the second week of a six-week lockdown, while masks will be mandatory as of midnight on Wednesday.
By the numbers
* 484 new cases, the 17th consecutive day of a triple-digit increase and Victoria's worst day for new cases
* Two more deaths - two males in their 90s connected to aged-care settings - bringing the state's toll to 44 and the national figure to 128
* 205 people in hospital, with 40 in intensive care
* 6739 total cases in Victoria since the pandemic began
* 3408 cases are active; with 3305 in metropolitan Melbourne and Mitchell Shire and 103 cases in regional Victoria
* 1,385,964 tests have been done in the state, with 24,726 done on Tuesday
* Of the new cases, 97 are connected to known outbreaks and 387 are under investigation
* Victoria's previous highest daily total cases of 428 was on Friday, July 17
