Officers had recommended that the proposed first floor extension at the Mohamaddi Mosque in Netherfield Road, Nelson, be rejected on highway safety grounds.
But Mr John Clancy, speaking on behalf of the applicants, said that usage of the mosque would not increase significantly as a result of the extension. People were currently "squashed in like sardines", he said.
The extensions include the relocation of a prayer room and teaching facilities and the use of the existing first floor as a ladies' prayer room.
"The only grounds for refusal is a perceived increase in traffic. I must stress that the congregation will not increase. The mosque serves the local community, not the wider community. It is on the edge of the town centre and is on the site of a former chapel which held 400 people. The present congregation is nowhere near that number," said Mr Clancy.
Coun. Nadeem Ahmed said he did not think the use of a back street by traffic leaving the mosque would cause any problems. "Lorries from our Operational Services cause more damage to it," he said.
Members voted by an 8-2 majority to approve the application, with BNP councillors Brian Parker and Adam Grant being the only ones to back the officer's recommendation of refusal on highway safety.
Because the decision is deemed a major diversion from officer recommendation, the matter will be referred to the council's Development Control Committee for a final decision.