English ruled out the introduction of income-testing for Super, saying "that issue had been settled many years ago".
"New Zealand had 30 years of debate over means-testing and came to the conclusion not to do it.
"One of the things that seems to occur as a result of that is a significantly increased number of older people in work because they can still retain their National Super in full even though they are working.
"It's turned out that has happened on a larger scale than is expected."
One of the other proposed changes to make Super more affordability is to change the way it is "indexed", such as by linking payments to inflation, as benefits are.
But English also ruled this out, saying there would not be any change to entitlements.
He would not comment on a proposal by United Future Peter Dunne's Flexi-Super proposal, which would allow people to take a lower amount of Super at age 60 or a higher amount at age 70.
The Maori Party has also proposed lowering the eligibility age to 60 for Maori and Pacific Islanders, but English said this was not on the table.
English's talk of resetting superannuation has been criticised by New Zealand First and Labour, who oppose a higher eligibility age.
Labour leader Andrew Little said English needed to "come clean" about his plans for Super because his comments have set off "alarm bells" for New Zealand households.
Labour and New Zealand First want to restart Government contributions to the Super Fund as soon as possible, while National plans to restart them in 2020/21.
Experts say the Government will have to do more than raise the age of eligibility to keep the Super scheme affordable. It would also have to consider means testing or changing the payments. Retirement Commissioner Diane Maxwell has also proposed raising the residency requirement from 10 years to 25 years.
The cost of the scheme is expected to triple in the next 20 years from $11 billion to $36b as more people reach the over-65 age-group and live for longer.
Deleted tweet
English also faced questions this morning about why a relatively innocuous tweet was deleted from his official Prime Ministerial Twitter account.
The tweet, sent yesterday, said: "We're committed to making the right decisions to make sure New Zealand's prosperity is sustainable for the long term".
Asked on TVNZ's Breakfast why it was deleted, English said he was not aware of what had occurred or why his staff had removed the tweet.
"I'm changing phones so I don't have Twitter. So I can't see what is on my Twitter right at the moment."
When it was pointed out that US President Donald Trump controlled his own Twitter account, English said: "That might be why I don't have control of it."