Diligent signed 122 net new client agreements in the September quarter, down from 168 in the same quarter last year, the company says.
It is the software firm's fifth successive quarter of slower net new client growth.
Diligent says it can not report any financial results until it has sorted out its accounting issues.
The company is having to restate its accounts for the 2010, 2011 and 2012 financial years and until it has done that, it can not provide any financial information for this year.
Milford Asset Management analyst Mark Warminger says the information Diligent has released suggests the company's sales effort is losing momentum.
"Not only is there slower growth here, they actually did make specific comments saying that new sales growth in the US in the third quarter was slower than expected. They also said new sales growth in other parts of the world as well was slower than expected .... it does seem as though they're finding it harder and harder to find new clients."
Mr Warminger said the company reported that upgrades - or current clients taking more of the same product - remains strong.
Diligent shares fell as much as 65 cents to $5 in morning trading.
