The Shareholders Association says an analysis of 47 publicly-listed companies indicates that nearly half of them are in distress, and are at risk of defaulting on their loans.
Association chairman Bruce Sheppard says it appears 20 of the companies analysed, have debt levels close to, or beyond that, which saw Nuplex breach its banking covenants and forced it to raise capital from investors.
Mr Sheppard would name the companiess, saying he would write to then first seeking an explanation.
He said they are not necessarily the larger ones on the stock exchange.
A number of companies have raised money recently to strengthen their balance sheets, including Fletcher Building, Nuplex, Freightways, and Kiwi Income Property Trust, though only Nuplex did so after breaching its banking covenants.