UN chief Ban Ki-moon also condemned the plan, saying it could torpedo efforts to broker a deal to end the three-year civil war, which has killed 150,000.
Syrian government forces have made gains recently, but rebels still control vast territories. It is unlikely that voting would be held in those areas.
President Bashar al-Assad is expected to seek a third seven-year term.
The government recently framed an election law that stipulated all candidates must have lived in Syria for the past 10 years.
Most opposition leaders have fled the country, so are in effect barred from standing.
Opposition activist Ahmad Alqusair accused Bashar al-Assad of “holding elections over the blood of Syrians” and said only the president’s supporters would vote.
“If we are being blockaded from even eating bread, how can I vote,” he told the Associated Press.
One government lawmaker said there would be no voting in rebel-held areas, but no official announcement has yet been made.
The US, EU and UN were united in condemning the planned vote.
“Calling for a de-facto referendum rings especially hollow now as the regime continues to massacre the very electorate it purports to represent,” said state department spokeswoman Jennifer Psaki.
Ban Ki-moon warned that it would “damage the political process and hamper the prospects for a political solution”.
And both the EU and the US labeled it a “parody of democracy”.
Parliamentary speaker Mohammed al-Lahham announced the election, and said overseas Syrians would be able to vote from May 28.
It is unclear how the government plans to organize voting in contested areas, or how the six million people who have fled their homes could register.
Also, more than 2.7 million Syrians are living as refugees in neighboring countries, and many other expatriates live in countries where Syrian embassies have been closed since 2011.
The announcement came just hours after mortar shells exploded about 300ft from the parliament building in central Damascus, killing five people, according to state TV.
President Bashar al-Assad succeeded his father Hafez al-Assad in 2000 and was re-elected in 2007, taking 98% of the vote in a referendum.
He has not said publicly whether he will stand, however, no-one doubts that he will seek a third term.
Amendments to the constitution approved in a widely criticized referendum in 2012 mean that there can be multiple candidates in the election.
However, it is unlikely that anyone will seriously challenge Bashar al-Assad.
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