Foreign ownership in New Zealand's privately-owned companies is nearing half.

Photo: NZX / Supplied

Figures compiled by Bill Rosenberg for the Campaign Against Foreign Control of Aotearoa show foreigners owned 47 percent of shares in firms in the year to March 2016, up from 37 percent the year before. That is the highest level since 2002, when it hit 60 percent.

Dr Rosenberg said while foreign investment can bring money, technology and jobs, evidence showed New Zealand lost more than it gained.

"New Zealand has a moderately high degree of overseas ownership. We're dependent on it in some quite critical areas such as finance.

"The quality of investment here is not great, and a lot of our income is sent overseas," he said.

Some $16.3 billion in profits and investment income left this country in the year to March 2016, and Dr Rosenberg said over the past decade this had averaged more than the combined dairy and forest product exports.

More than $2 out of every $5 - $6.8bn - went to the mainly Australian owners of New Zealand's banks.

"There is a big cost to New Zealand in all of this. We need to make sure ... we're getting a good return from it in terms of jobs, and increasing the value we're getting out of our products and exports."

Dr Rosenberg said stronger controls over foreign investment were needed to make sure New Zealand could build a high growth, high wage economy.

"We need a reformed Overseas Investment Office that has much stronger rules and has better resources."

In terms of wealth such as housing, land and financial assets, foreign investors owned 28 percent, or $386bn, of the $1.4 trillion of wealth in New Zealand at March 2016, similar to the previous year.