Nadia Eweida, a check-in worker at Heathrow Airport, told the Daily Mail she was suing the airline for religious discrimination after being sent home for breaching BA's dress code.
"British Airways permits Muslims to wear a headscarf, Sikhs to wear a turban and other faiths religious apparel. Only Christians are forbidden to express their faith," Eweida was quoted as saying.
British Airways said company policy said employees must wear jewelry, including religious symbols, under their uniforms.
"This rule applies for all jewelry and religious symbols on chains and is not specific to the cross," the airline said in a statement.
"Other items such as turbans, hijabs and bangles can be worn as it is not practical for staff to conceal them beneath their uniforms."
Liberal Democrat lawmaker Vincent Cable, who represents Eweida's home area of Twickenham in west London, said it was "absolutely mind-boggling that Britain's flag-carrying airline could treat its employees in such a disgraceful and petty manner."
"Nadia is a devout Christian who was displaying her faith, but in a modest and totally unprovocative manner," he said.
"It is absolutely right that other religious minorities be allowed exemption from the dress code, but why can't a Christian be treated in the same way?"
Religious symbols and dress have been a hot topic of debate in Britain since former Foreign Secretary Jack Straw sparked controversy last week by saying he asks veiled Muslim women to uncover their faces when he meets with them.