"The SuperGold Card is yours - you have earned it - but please, in your own interests, fight to keep it."
New Zealand First introduced the SuperGold card in 2007, while the party's SuperGold Health Check bill went before Parliament this year but was defeated 61 votes to 60.
"The intention of the bill was to provide three free GP visits with the SuperGold Card each year," said Mr Peters.
"New Zealand First didn't want our seniors sitting at home feeling ill and worried about going to a GP because of the cost."
He advised his audience to ask businesses to offer discounts for gold card holders, noting that his own hairdresser gave him a discount.
"He gives a one-third discount to gold card holders and he profits from it because he gets a lot more customers."
The audience was urged to fight for the card because he said they had paid taxes over years when tax rates were high.
"All Grey Power members must tell the government 'Hands off our SuperGold Card'." And he said they should also refuse to buy smartcards for public transport.
Talking about the impact of immigration on senior citizens, he said people in Whanganui were paying for the Auckland infrstructure overburdened by high numbers of migrants.
"You may think it has nothing to do with you but it does - you are paying for it."
Mr Peters also talked about the impact of high immigration on health services and said "large numbers of immigrants" were visiting hospitals rather than going to GPs.
"If New Zealand taxpayers, who have paid taxes all their lives, go to hospital they have to join a queue comprising a large number of immigrants who have been in the country five minutes."
He said the strain on services impacted in Whanganui because all district health boards were underfunded.
Mr Peters did not have time to answer questions because he arrived late due to his flight being delayed, but he promised to answer questions sent to his office.