HANOI, Jan 7 (Reuters) - Vietnam's ruling Communist Party has expelled General Tran Do, a prominent life-long revolutionary but increasingly outspoken critic, a party source said on Thursday.

The source said the party's ideology department had issued an internal statement that said Do-- who has called for sweeping political reform in Vietnam-- had been ousted with immediate effect.

A long-time party member who was formerly head of ideology at the Commission for Culture, Literature and the Arts, Do has become a persistent thorn in the side of the Communist Party since the first in a series of letters he penned leaked out a year ago.

Late last year, Communist Party General Secretary Le Kha Phieu went to Do's central Hanoi home for a lengthy meeting with the former general, sources have said.

The sources added that Phieu told Do that his views were not in line with official policy but that the party was ready to listen to what he had to say.

Do's expulsion comes just weeks before the powerful party central committee is expected to meet for a crucial plenum that is expected to announce a reshuffle within the elite 19-person politburo, sources said.

Dissenting political views are rarely tolerated in communist Vietnam, and long jail terms have been given to people who have publicly criticised the party or called for fundamental political reform.

In his essays, which were normally addressed to the country's leaders and often open, Do issued vociferous calls for greater democracy in Vietnam.

Last June he called for frank debate on the future role of the ruling party and said the country must be prepared to cast aside socialism if that would help Vietnam's development.

"Do we need a developed country with enough food and clothes, freedom and happiness (i.e. democracy)...or do we need a country with socialist orientation that is very poor," said Do.

"A choice must be made. I myself chose a Vietnam with 'people enjoying adequate food, clothes, freedom and happiness', with or without socialism," he added, quoting Vietnam's late revolutionary leader Ho Chi Minh.

Premier Phan Van Khai, who ranks third on the party politburo, has said that Do and other intellectuals who have attacked socialist-inspired policies and the party's monopoly on power, were entitled to their views.

But Do has previously complained of intimidation of himself and his family, a slur campaign against him in official media, and surveillance and questioning of visitors to his house.

"I clearly see that there is a psychological war aimed at killing my political life," he said in one letter.

Do retains his respect for Ho Chi Minh (*), but has said the party must change with the times and while strict discipline and absolute leadership were key to wartime successes, these methods were now obsolete.

"In peace...those strong points have created a lack of democracy within the party and society. Those strong points are making the party become an authoritarian ruling party," he wrote last year.