Its foreign buyers policy would be allowed under the China FTA, which the party signed in 2008.
However, the South Korea FTA National agreed this year contained additional commitments around free investment, and those will eventually need to be included in the Chinese agreement.
While some believe the Korean agreement contains enough flexibility to allow the regulation of overseas purchases of land and housing, Labour's trade spokesman David Parker said it could create the risk of South Korean claims.
Neither China or South Korea is involved in TPP negotiations, but Mr Parker said Labour's understanding was that the aspect of the South Korean agreement that it viewed as problematic was in the TPP text.
Mr Parker said the TPP, which has been negotiated since March 2010, includes countries representing 40 per cent of world GDP, but its impacts were not known or able to be accurately debated.
"Everyone knows they can't disclose the actual text. But when New Zealanders are marching in the streets in their thousands...the Government has a duty, in my opinion, to properly inform New Zealanders what is happening."
The deal includes intellectual property rights, foreign investment rules, labour and environment standards, procurement policies, state-owned enterprises and competition, and disputes procedures.
Asked if some MPs pushed for Labour to oppose the TPP entirely, Mr Parker said he would not reveal what was said in caucus, "but that letter [outlining Labour's conditional support] is a caucus letter".
"We have a pretty long history supporting fair and free trade, including the likes of the China FTA. So we have not changed from that position."