A leading polling expert has said he would be very surprised if a majority of people over the age of 65 do not vote to leave the European Union.
Professor John Curtice says older people are one of the "hardest nuts" for the Remain campaign to crack.
On Thursday the Treasury warned Brexit would leave pensioners worse off- a claim rejected by the Leave side.
Meanwhile a new EU poll suggests Remain and Leave are level pegging in Wales, with little change.
The poll has Remain at 40%, Leave at 39% and do not knows at 14%.
Prof John Curtice from the University of Strathclyde told BBC Good Morning Wales: "I will be very surprised if a majority of over-65s don't vote to leave the European Union."
He said: "There's quite a substantial difference between the views of younger voters and those of older voters on this subject.
"Amongst the 18-to-24 year olds, opinion polls suggest on average that maybe as many as three quarters of them are going to vote to remain.
"Conversely if we look at the over-65s, on average across all the opinion polls just over 40% of them only are going to vote to remain and the clear majority are going to vote to leave."
"Certainly the over-65s, the older people, are perhaps one of the hardest nuts, for the government, for the remain campaign to try to crack."
He suggested this was why "they've used the very last hours before purdah to try to come up with something that might persuade them to change their minds.
"The older you are the more you think about how life was 20, 30 or 40 years ago.
"Therefore perhaps you are somebody who is rather more resistant, rather more reluctant, rather more uncomfortable, with the consequences of the immigration that seems to be associated with European Union membership."
The purdah period before the June 23 referendum prohibits UK, Welsh and local government from publishing material relating to the referendum, although some exemptions apply.
A Wales-wide internet poll conducted by YouGov for Cardiff University's 2016 Welsh Election Study has put:
- Remain at 40% (-1% from the last YouGov Welsh Political Barometer Poll between May 2 and 4)
- Leave at 39% (no change)
- Do not knows or will not vote at 22% (+2%)
Prof Roger Scully of the Wales Governance Centre at Cardiff University said the polls "shows things are still very close in Wales, at least if the internet polls are getting it right".
- The Wales Election Study poll was conducted with 3,234 people from 6-22 May. The earlier Welsh Political Barometer poll was conducted with 1,326 people.