CANBERRA—A Liberal senator has promised to wear a south Vietnamese freedom tie in parliament in protest at a communist party official's visit to Australia.

Prime Minister Kevin Rudd will host an official dinner at Parliament House on Monday night, which includes the general secretary of the central committee of the Communist Party of Vietnam, Nong Duc Manh.

Addressing a rally of about 200 people in the rain outside Parliament House, Senator Gary Humphries promised to wear a yellow south Vietnamese freedom tie in parliament on Monday.

The former ACT chief minister said Australia needed to protest at Vietnam's lack of democratic and religious freedoms.

"The arrival of the general secretary of the Communist Party of Vietnam is a very important opportunity for the Australian government to make a very important point to the government of Vietnam," he said.

"And that is its failure to provide democratic institutions to its people, its failure to free dissidents from its jails, its failure to provide freedom to the Buddhist church of Vietnam are all unacceptable."

Senator Humphries was among the official party at the RAAF Fairbairn base in Canberra which met with Mr Nong on Sunday.

"And I met the general secretary when he got off his plane and I have to say he was very interested in the tie I was wearing, the same tie I'm wearing today.

"He looked at the tie and he looked at me. I think he was a bit dubious about my tie."

Vietnamese Community of Australia federal president Phong Nguyen, who led the rally, said the Australian government had brought disrespect and shame by allowing a Vietnamese communist party official to visit.

"This house is a parliament of elected representatives yet our prime minister, our government, has lowered themselves to the level of giving a state visit to a person who is not elected, not represented.. . by the people of Vietnam," he said.

On more optimistic note, Senator Humphries said Vietnam, one of less than half a dozen communist nations, would one day become a democracy.

"I'm very confident ladies and gentlemen, very confident, that this process will one day lead to the destruction of this regime in Vietnam," he said.