Venezuela's Supreme Court on Monday rejected the opposition's latest bid to cut short the term of President Nicolas Maduro, whose opponents blame him for a severe economic crisis.
The court ruled that a constitutional amendment proposed by opposition lawmakers could not be applied retroactively or immediately to Maduro's current term as the bill proposed.
It said that would violate "the will of the people" who elected him.
The opposition vowed to oust Maduro when it took control of the legislature in January after winning elections.
Lower house lawmakers last week approved on a first reading a bill proposing to reduce presidential terms from six years to four. That bill would also have to be approved in a referendum to enter into force.
The court said in its ruling on Monday that "trying to use a constitutional amendment to cut short immediately a term of office of someone popularly elected, such as the president of the republic, is an act of fraud against the constitution."
The opposition leader in the legislature, Henry Ramos Allup, denied that the amendment was unconstitutional and criticised the court for vetoing it before it had a second reading.
"You are the ones committing constitutional fraud," he wrote on Twitter, branding the Supreme Court judges "outlaws."
Recall referendum drive
Maduro has successfully blocked previous bills in the National Assembly by appealing to the Supreme Court, which critics say he controls.
Attacking Maduro on another front, the opposition has also tried to call a direct referendum on whether to remove him from office.
Maduro reached the halfway point of his six-year term last week. Under the constitution he can now be removed from office in a recall referendum, which the opposition hopes to do by the end of the year.
Electoral authorities have so far blocked that bid too, however.
Maduro's critics say he also controls the electoral board. The opposition has called for demonstrations in front of its offices across the country on Wednesday.
Maduro has vowed to hold on to power and press on with the socialist "revolution" launched by his late predecessor Hugo Chavez.
Venezuela's economy has plunged along with the price of the oil on which it relies for foreign revenues.
Citizens are suffering shortages of medicines and goods such as toilet paper and cooking oil.
On Monday, the government started turning off the electricity supply in its 10 most populous states for four hours a day to deal with a severe power shortage. It said the measure would last for 40 days.
The country's biggest brewery, Cerveceria Polar, said last week it will stop producing beer because it is running short of barley.
The cash-strapped government is unable to meet businesses' demand for the dollars it needs to buy goods and materials abroad.
The import-dependent economy contracted 5.7 percent last year, its second year of recession. The official inflation rate was recorded as more than 180 percent but private analysts say the real rate was several times that.