The body which claims to be the voice of Britain's Muslims has told women that wearing the veil is "not open to debate".
The statement will add to controversy about the veil
The Muslim Council of Britain (MCB) said that not covering the face is a "shortcoming" and suggested that any Muslims who advocate being uncovered could be guilty of rejecting Islam.
In a statement published on its website the MCB, warns: "We advise all Muslims to exercise extreme caution on this issue, since denying any part of Islam may lead to disbelief.
"Not practising something enjoined by Allah and his Messenger… is a shortcoming. Denying it is much more serious."
The statement quotes from the Koran: "It is not for a believer, man or woman, that they should have any option in their decision when Allah and his Messenger have decreed a matter."
The statement will add to controversy about the veil after France earlier this week banned the full-face covering.
"There is no case for a French-style ban in the UK and virtually no serious person supports it," said Haras Rafiq, of the moderate Muslim think-tank, Centri.
"But by this statement, effectively suggesting that the veil is an obligation, the MCB have put themselves at the opposite extreme of the spectrum."
The statement is signed by the MCB's then secretary-general, Mohammad Abdul Bari, and his deputy, Daud Abdullah. It was published in the wake of an earlier controversy about the niqab but passed without notice.
It remains available on the MCB website as a statement of policy.
Other signatories of the statement include Imran Waheed, spokesman of the extremist group Hizb ut Tahrir and several other extremists including Haitham al-Haddad, who has denounced music as a "prohibited and fake message of love and peace". All 27 signatories, who describe themselves as "Islamic groups and scholars," are male.
Dr Bari stepped down as secretary-general of the MCB last year, but remains chairman of the hardline East London Mosque, whose chief imam, Abdul Qayum, also signed the statement.
Dr Bari is also a former president of the fundamentalist Islamic Forum of Europe, which controls the mosque and which advocates a sharia state in Europe.
The MCB received significant funding under the previous government and was seen as the main representative voice of Britain's estimated 2.8 million Muslims but has not received any official money since February 2010.
The MCB did not respond to enquiries.