Prime Minister Hun Sen on Wednesday accused opposition leader Sam Rainsy of betraying the country by publishing a “false map” on his party’s Web site.

The Sam Rainsy Party has put a “French-era” map from 1952 on its Web site, which it claims marks the proper border between Cambodia and Vietnam. The map reflects the borders that are filed with the UN but are not the reality on the ground, according to the party.

However, Hun Sen said on Wednesday the map was false.

“The government must take legal action against the fake map, because it is a fake public document,” Hun Sen told a gathering of graduates at the Royal University of Phnom Penh. “When we are defending against an invasion from the west and you set up a fake map of the east, I accuse you of betrayal.”

Hun Sen was referring to a protracted military standoff with Thailand. Sam Rainsy Party members have said Cambodia is losing land to Vietnamese encroachment. The issue of encroachment from either of Cambodia’s neighbors is a political flashpoint.

Sam Rainsy, who is currently in France and facing a jail sentence if he returns, said by video conference Wednesday the map posted on his Web site “is not fake.”

“But the government is afraid of the correct map,” he told reporters. “So Prime Minister Hun Sen’s reaction to my map on the Web site is wrong. This map helps protect Cambodian sovereignty.”

Meanwhile, Hun Sen is scheduled to visit military troops in Battambang province along the Thai border on Saturday.