AN opposition group has announced it will not field candidates in next month's parliament by-election.
National Democratic Action Society (NDAS) contested parliamentary elections in 2006 and last year, but never won a seat.
Eighteen seats are up for grabs after as many MPs representing another opposition group, Al Wefaq National Islamic Society, resigned in March in solidarity with anti-government protesters.
However, NDAS says it will not field candidates, while its secretary-general Ibrahim Sharif is in prison.
Mr Sharif was jailed for five years by the Lower National Safety Court in June in connection with a plot to overthrow the regime.
"He is our leader in detention," said NDAS deputy secretary-general Redha Al Mousawi.
"His absence calls for society members not to contest by-election."
He also pointed to ongoing instability in vacant constituencies.
"The 18 constituencies that are vacant and open for elections are facing regular unrest.
"This is the same situation in the villages, so how can a political society or an individual contest in these areas?"
Al Wefaq is yet to announce whether it will seek re-election in the 18 constituencies it vacated.
It is understood no agreement has yet been reached by the society's decision-making council on whether to take part in the September 24 by-election.
Meanwhile, NDAS said it had forwarded details of arson attacks on its branch in Arad, headquarters in Umm Al Hassam and the home of its senior member Dr Munira Fakhro in March to Bahrain Independent Commission of Inquiry.
Both NDAS and Al Wefaq were part of an alliance of seven opposition political groups formed in February that refused any dialogue with the government until certain conditions were met - including guarantees of a new constitution and an elected government.