Strictly Orthodox leaders have pledged to organise mass protests against plans by Queen Mary, University of London, to build on the site of a Jewish cemetery in Mile End Road, east London.

The Committee for the Preservation of Jewish Cemeteries in Europe is leading the campaign against the development of the Novo Sephardic cemetery, which now belongs to the university. Planning permission has been approved and construction has started.

Thirty years ago, the land was sold to the college by the Spanish and Portuguese Jews' Congregation on a 999-year lease. The sale involved exhuming thousands of graves and moving the remains to a site in Brentwood, Essex, prompting fierce protests from strictly Orthodox community. A quarter of the graves were left undisturbed in the college grounds.

The latest development is to allow the widening of the path from Mile End Road to the campus and creating a "space for silent contemplation" by the law and humanities buildings. The preservation group believes the work will affect burial sites. The Sephardi organisation disagrees and its Rabbi Eiran Davies is supervising the scheme.

QMUL director of estates Simon Neal said: "The cemetery has been quite neglected - it was effectively a piece of wasteland." He maintained the plans would improve the site, and the contemplation area would include information about the cemetery and the East End Jewish community.

"We know mistakes were made in the '70s and both us and the SPJC are trying to put them right. We have worked very closely with them."

However, the preservation group's executive director, Rabbi Abraham Ginsburg, said community concerns had been not been answered and claimed Queen Mary principal Simon Gaskell had refused to meet representatives.

"It is disgraceful that the cemetery was ever sold for financial gain in the first place. We have evidence that there are more than 100 children's graves on the site.

"We know we do not have much power to change the plans. But it is a total violation of Jewish law. We cannot just turn a blind eye. I have dealt with cases of Jewish cemeteries in Eastern Europe and have had more problems getting to speak to the owners here in London than I do over there. It's totally unacceptable and disrespectful."

Mass protests would be organised when the academic year starts. "There are many Jewish students at the university. We must get them on board."