The former Foreign Affairs Minister, Sir Don McKinnon, says it would be disruptive for New Zealand if Britain leaves the European Union (EU).
British voters go to the polls on Thursday to vote in a referendum on whether to stay in the EU.
Sir Don, who lived in Britain for 10 years while he was Commonwealth Secretary-General, said he hoped Britain would vote to stay.
He told TVNZ's Q + A programme the decision would not be as significant for New Zealand as Britain's initial decision to join the European Community in 1973.
Sir Don said all exports to European Union countries currently go through Brussels, so some agreements for Britain might need to be changed.
"Yes it could have an effect but we're not of the same dependency as we were 30 or 40 years ago, when it was just a huge market for New Zealand.
"But it would be disruptive."
An Institute of Economic Research (NZIER) study said the post-Brexit picture was "horribly murky", but if Britain voted to leave the European Union, New Zealand's exports would fall by an estimated $190 million a year.
Meanwhile, Britain's right-leaning Mail on Sunday newspaper today endorsed the campaign to remain in the European Union.
But the Sunday Telegraph, also right of centre, came out for "Leave".
The latest polls show a shift towards the UK staying in the European Union, with little between the sides.
In France, the economy minister said leaving the European Union would make the UK as significant as Guernsey.
Emmanuel Macron told Le Monde newspaper that Britain would become "a little country on the world scale [that] would isolate itself... at Europe's border".
He said the EU should send "a very firm message" about the consequences of a British vote to leave the bloc.