Newham councillor Alan Craig last night accused Tablighi Jamaat, the controversial Islamic sect behind plans for a giant mosque near the site of the 2012 Olympics, of breaking its promises about keeping local people informed.

He called on them to "immediately come clean with their plans".

Tablighi Jamaat says that the mosque will include a 12,000-capacity prayer hall, a conference centre and an Islamic school as well as a library, an Islamic garden and living quarters.

Cllr Craig criticised the group for not being more transparent with the details of its proposals for the mosque, saying that enquiries to its public relations advisers, Indigo Public Affairs, had "regularly drawn a blank".

He also criticised the group for failing to meet their promise of a "Work in Progress" open day this summer.

"Tablighi Jamaat pledged an Open Day event during the summer at which we would view the work, see an exhibition and meet their architects and consultants," said Cllr Craig who is leader of the Christian Peoples Alliance group on Newham Council. "It is now almost the end of summer with the Islamic fasting month of Ramadan just two weeks away, yet there is still no sign of the event."

He continued: "In March they indicated to local residents and media their serious intent to press ahead with their mosque but refused to answer questions or give details," said Alan Craig. "So five months later worried locals are left with the threat of this huge mosque hanging over their heads yet still are given no information."

Tablighi Jamaat has also come under fire from moderate Muslims. Dr Taj Hargey, of the Muslim Educational Centre of Oxford, accused the group of espousing a virulent intolerant form of Islam that will "generate social friction rather than community cohesion", whilst Dr Irfan al-Alawi, of the Centre for Islamic Pluralism, accused the group of being linked to terrorist activities in Pakistan and Britain.

"Tablighi Jamaat is a secretive global missionary sect from South Asia that wants to build its international headquarters mosque here in London," said Cllr Craig. "Yet they will not enter into discussions or explanation of their plans.

"This silence is not golden. It represents yet another false claim and broken promise by Tablighi Jamaat."