The 42-year-old said after last week's Humana Challenge he was considering making "drastic changes" because of spiking federal and state tax rates but on Tuesday he said he should have kept his thoughts to himself.
"Finances and taxes are a personal matter and I should not have made my opinions on them public," Mickelson said in a statement released by his management company.
"I apologise to those I have upset or insulted and assure you I intend to not let it happen again."
Mickelson, a 40-times winner on the US Tour, has piled up career earnings of more than $67 million and considerably more via corporate endorsements and his golf course design company.
According to Forbes magazine, the American left-hander earned $43 million in endorsements in 2012, second only to Tiger Woods among golfers and seventh among all athletes.
"Well, it's been an interesting off-season, and I'm going to have to make some drastic changes," Mickelson said after tying for 37th place at 17-under at the Humana Challenge on Sunday in his first tournament of the season.
"I'm not going to jump the gun and do it right away, but I will be making some drastic changes. I happen to be in that zone that has been targeted both federally and by the state and it doesn't work for me right now."
California voters in November approved Proposition 30, which raised state income tax to 13.3 percent on earnings of $1 million or more, a 29.13 percent increase over the previous "millionaires" tax of 10.3 percent.
Mickelson will also be affected by the rise in the top bracket of the federal tax code where rates have gone up from 35 percent to 39.6.
Hinting that he might even leave his home state of California, Mickelson said on Sunday: "If you add up all the federal and you look at the disability and the unemployment and the Social Security and the state, my tax rate's 62, 63 percent, so I've got to make some decisions on what I'm going to do."
Asked whether his decision last month not to get involved with the new ownership group of the San Diego Padres baseball team had been linked to tax issues, he replied: "Absolutely."
Mickelson had planned to elaborate on his feelings during a news conference scheduled for Wednesday on the eve the Farmers Insurance Open at Torrey Pines, outside his native San Diego.
However, he decided to act earlier with a statement.
"I'm like many Americans who are trying to understand the new tax laws," Mickelson said. "I've been learning a lot over the last few months and talking with people who are trying to help me make intelligent and informed decisions.
"I certainly don't have a definitive plan at this time, but like everyone else I want to make decisions that are best for my future and my family.
"I absolutely love what I do. I love and appreciate the game of golf and the people who surround it. I'm as motivated as I've ever been to work on my game, to compete and to win championships."
Many US Tour professionals are based in either Florida or Texas, two states which do not charge state income tax.
Former world number one Woods, like Mickelson a native of Southern Californian, left his home state after turning professional in 1996 and relocated to Florida where he has remained ever since.
"Well, I moved out of here back in '96 for that reason," Woods said at Torrey Pines on Tuesday when asked for his reaction to Mickelson's comments about the high tax rates in California.
"I enjoy Florida, but also I understand what he was, I think, trying to say. I think he'll probably explain it better and in a little more detail."