Mr Groser owns 40,000 shares in Uruguayan company New Zealand Farming Systems Ltd, which uses Kiwi technology to develop dairy farms.
He hasn't broken any of Parliament's rules but Labour says he should sell the shares because there could be a conflict of interest.
Mr Groser told TV One News last night he had made no attempt to conceal his shareholding and had met Parliament's financial reporting requirements.
Prime Minister John Key said the Cabinet Office supported Mr Groser's assurance and he was "absolutely, 100 percent comfortable" with the minister's position.
But Labour MP Darren Hughes says that with the shares valued at 55 cents Mr Groser has a significant investment worth about $22,000 and the minister is too close to the action.
Mr Groser recently visited Uruguay and met representatives of the company, but he says there was no way he could have influenced the share price to his own benefit.
