The Civil Court has ordered the United Front for Democracy against Dictatorship to partially lift its blockade of Government House so officials can enter the compound.
The Prime Minister's Office sought the court's intervention to dissipate the UDD rally's growing momentum on the back of deposed prime minister Thaksin Shinawatra's daily phone-ins to protesters.
The injunction orders the red shirt protesters to remove their blockade on Luk Luang road, from Thewakam intersection to Chamai Maruchet bridge, and to allow access to Government House through gates six and eight.
UDD leader Jatuporn Prompan said they would appeal the injunction and urged the demonstrators to stay put.
Prime Minister Abhisit Vejjajiva has not ruled out using "decisive measures" to disperse the rally.
But the Government would only break up the demonstration if the UDD broke the law, Mr Abhisit said before leaving for the G20 summit in London.
"If people exercise their rights without breaking the law, or affecting national security, the Government will not take any action which could be distorted," he said.
"This is to make everyone understand that use of decisive measures will only be done under the rule of law, and in line with international practices. They will only be taken if it becomes unavoidable," Mr Abhisit said.
He said the Government would not fall for tactics aimed at increasing the political turmoil and provoking violence before the Songkran break.
Thaksin said on Monday he would return tomorrow to join his supporters if the Government used force to break up the rally.
"Those who break the law will be arrested immediately," said Deputy Prime Minister Suthep Thaugsuban, the Government leader in Mr Abhisit's absence.
The rally, which is in its seventh day, forced the cancellation of yesterday's cabinet meeting. The Government will move to a temporary office next week if the protesters continue to block Government House, said Interior Minister Chavarat Charnvirakul.
The Somchai Wongsawat administration was forced last year to use Don Mueang airport as a temporary office when the yellow-shirt People's Alliance for Democracy occupied Government House.
The UDD is now using similar tactics against the Democrat led coalition Government.
The red shirts' rally will not be sufficient to obtain its goal of destabilising the Government, Deputy Interior Minister Boonjong Wongtrairat said.
The ministry has ordered local Government agencies, including village chiefs, to closely monitor the UDD's activities around the country to prevent clashes between the red shirts and the yellow shirts, he said.
Dozens of former executives from the dissolved Thai Rak Thai and People's Power parties have joined the rally and will go on stage on Friday, after Thaksin's call on March 27 for the 111 banned former TRT executives to join the protest.
A UDD source said the group would campaign for the reinstatement of the 1997 charter, abolished by the 2006 coup makers.
Yesterday, heavy rain dampened the red-shirt turnout which fell to 5,000 people.
Mr Jatuporn said the UDD would not quit until Privy Council president Prem Tinsulanonda and the Prime Minister resigned from their posts.
In a related development, authorities have agreed to strip Thaksin of his police lieutenant colonel rank, a police source said
The source said the move would force Thaksin to return his royal decorations.
The action was being taken because Thaksin was sentenced to two years in prison after the Supreme Court last year found him guilty of abusing his authority in connection with the Ratchadaphisek land scandal, the source said.
Source - The Bangkok Post