Brown asked why the government should be approving new coal mines while trying to lower carbon emissions through a new carbon tax.
"Shouldn't we be making sure we do have secure and growing food production for a planet that's heading for nine to 10 billion mouths to feed in three or four decades?" Brown said in a speech to the National Press Club.
"We need to be reviewing this. I think when it comes to land ownership in this country, like New Zealand, we should have a registration of foreign ownership.
"And here we've got in Australia governments at state and federal level who are saying coal first over food production."
Assistant treasurer Bill Shorten, who authorised Foreign Investment Review Board approval for the purchase of the agricultural land in NSW, said he was advised by the state government to give the go ahead.
The NSW government had granted exploration licences to Shenhua for the Watermark area in 2008, with the company pledging to invest up to $675 million into the state, he said.
Shenhua plans to mine 1 million tonnes per annum of coal from Watermark in 2013, up to 4Mtpa in 2014 and 7Mtpa by 2015.
Brown said he didn’t object to Shenhua being granted approval to mine coal on agricultural land only because they are a foreign company.
"When it comes to the land being taken over, I don't care (whether) it's Shenhua or whether it's one of our great Australian corporations," he said.
"What worries me is that it's happening on the Liverpool plains – it's the small farms of some four, five, six, seven generations of ownership being put out of business for a 20 to 30-year coal mining venture, which is going to make the future of farming in the whole Murray-Darling Basin … much more problematic."
Shenhua has enlisted the support of New South Wales Deputy Premier Andrew Stoner to approve its controversial $1 billion open cut coal mine near Gunnedah, despite resistance from local farmers.
Stoner allegedly contacted the Department of Regional Infrastructure arguing the case for Shenhua, saying the project was “state significant” and “of a high priority”, according to information obtained by a call for papers by the Greens in the NSW upper house.
In another email, consultants acting for Shenhua reminded NSW Director-General of Planning Sam Haddad of the financial commitments it had made to the state government, the local council and the Gunnedah community.
Greens MLC Jeremy Buckingham has tabled 1000 documents that outlined exchanges between Shenhua and the Coalition.
Shenhua is also being encouraged to develop another coal mine in the Illawarra or the southern highlands of NSW to justify exporting coal through Port Kembla after it missed a deadline to secure access at the Port of Newcastle.
The company, which is awaiting approval for its Watermark mine in the Liverpool Plains in the northern part of the state, could end up railing thermal coal from the mine past Newcastle and Sydney to Port Kembla, under a plan being considered by the NSW Department of Primary Industries.
Shenhua would need to contribute funds to significant infrastructure upgrades, which would only be feasible if it had a second mine in the south.
The company has held talks with the state government, Port Kembla Corporation and NSW Industry and Investment representatives to canvass the options available to get its steaming coal to port and on to power stations back in China, according to documents obtained by the NSW Greens.