Burma has issued a law which will bar pro-democracy leader Aung San Suu Kyi from taking part in planned elections and could force her party to expel her.
The new law prohibits anyone with a criminal conviction from belonging to a political party.
Ms Suu Kyi has been detained on various charges for most of the past 20 years, after winning the last polls in 1990.
She was already excluded from political office by a constitutional bar on people with foreign spouses.
The Political Parties Registration Law was published in official newspapers as part of a series of daily announcements of laws intended to guide the elections.
The deputy chairman of Ms Suu Kyi's National League for Democracy (NLD) said the laws were "too much".
"This is politically motivated toward Daw Aung San Suu Kyi," Tin Oo told reporters.
No date has yet been set for polls, which the military has promised to hold this year.
The latest law orders any party to reject people who are "not in conformity with the qualification to be members of a party".
It also bans members of religious orders and civil servants from joining political parties. Buddhist monks were the driving forces behind anti-junta protests in 2007.
The BBC's South East Asia correspondent, Rachel Harvey, says Ms Suu Kyi was already prevented from running for office because of her marriage to a British man, but it now seems she will be prevented from leading her own party or playing any role in election campaigning.
NLD spokesman Nyan Win said he was "extremely surprised" by the extent of the restrictions in the long-awaited legislation.
"I did not think it would be so bad," he told the AFP news agency.
Our correspondent says the NLD now faces a stark choice: expel its own leader in order to participate in the elections or opt out and forgo any further influence on the process.
She says the rules of the game are becoming clear. The question now is who will be willing to play.
Nyan Win said the NLD needed to "reply clearly" to the new regulations but had not yet decided how to respond.
"What I can say now is the law is meant to safeguard the constitution. It will be a very big problem for us as they asked us to obey a constitution that we cannot accept," he said.
Political parties have 60 days from Monday, when the law was promulgated, to register with an election committee.
A law made public on Monday made it clear that the commission members would be appointed by the junta.
The rules barring Ms Suu Kyi appear to fly in the face of recent calls by the US, European Union and Association of South East Asian Nations for the elections to be "inclusive".
The United States has reiterated its scepticism that any poll in which opposition figures are barred will have any credibility.
"We urge the authorities to begin a genuine political dialogue with all stakeholders as a first step towards credible elections," state department spokesman Philip Crowley told reporters.
"We are concerned by the Burmese authorities' unilateral decision to begin releasing the election laws without first engaging in substantive dialogue with the democratic opposition or ethnic minority leaders," he said.
"We remain sceptical that the elections planned for this year will be credible," he added.
Regional and international human rights organisations have documented continued harassment, persecution and detention of government critics.
The regime enacted five election-related laws on Monday, two of which have now been made public. Three more are to be unveiled in coming days.
Critics say the elections, the first to be held in Burma for 20 years, will be a sham designed to entrench the military's grip on power. - BBC