Heathrow check-in worker Nadia Eweida was sent home after refusing to remove the crucifix which breached BA's dress code.

Her treatment by BA - which styles itself as the "world's favourite airline" - brought condemnation both from Christian groups and members of other faiths last night.

BA's chief executive Willie Walsh has upheld the action against Miss Eweida for failing to comply with "uniform regulations" despite himself coming under fire recently for failing to wear a tie.

Miss Eweida, who has an unblemished record during seven years at BA, is suing her employer for religious discrimination after being suspended from work without pay for two weeks.

She said her treatment was all the more extraordinary as she and fellow employees had just undergone "diversity training" - including receiving advice from pressure group Stonewall on how to treat gays and lesbians in the workplace.

The airline's uniform code states that staff must not wear visible jewellery or other 'adornments' while on duty without permission from management.

It makes exceptions for Muslim and Sikh minorities by allowing them to wear hijabs and turbans.

Under rules drawn up by BA's 'diversity team' and 'uniform committee', Sikh employees can even wear the traditional iron bangle - even though this would usually be classed as jewellery - while Muslim workers are also allowed prayer breaks during work time.

But Miss Eweida, 55, from Twickenham, insisted her cross, which is smaller than a ten pence piece, was not jewellery but an expression of her deep Christian faith.

She questioned why she was being forced to hide her religion when BA's Muslim and Sikh workers could express theirs.

Miss Eweida said last night: "I will not hide my belief in the Lord Jesus. 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. I am a loyal and conscientious employee of British Airways, but I stand up for the rights of all citizens."

Her case comes at a time of intense debate over the rights of individuals to express their belief - following Jack Straw's call for Muslim women to remove their veils.

Earlier this month it emerged BBC governors had agonised over whether newsreader Fiona Bruce should wear a small cross on a chain around her neck while on air in case it might cause offence by suggesting a religious affiliation.

Miss Eweida, a Coptic Christian whose father is Egyptian and mother English, was ordered to remove her cross or hide it beneath a company cravat by a duty manager at Heathrow's Terminal 4 last month.

She then sought permission from management to wear the chain - but was turned down.

When Miss Eweida, who is unmarried, refused to remove the necklace she was offered the choice of suspension with pay or unpaid leave, pending a disciplinary hearing.

Following a meeting with her managers on 22 September 2006, Customer Service Manager Caroline Girling told Miss Eweida in a letter: "You have been sent home because you have failed to comply with a reasonable request.

"You were asked to cover up or remove your cross and chain which you refused to do.

"British Airways uniform standards stipulate that adornments of any kind are not to be worn with the uniform."

In a letter to Miss Eweida's MP, Vince Cable, last week, BA chief executive Willie Walsh insisted his employee had not yet been disciplined but said she was off work for failing to comply with "uniform regulations".

He added: "We have previously made changes to our uniform policy to accommodate requests, after a detailed evaluation process including Health and Safety assessment to incorporate the wearing of Sikh bangles."

But Miss Eweida said: "BA refuses to recognise the wearing of a cross as a manifestation of the Christian faith, but rather defines it as a piece of decorative jewellery.

"I would like to say how disappointed I am in this decision and the lack of respect shown by BA towards the Christian faith.

"I have been badly treated. I am a loyal and hardworking employee and for seeking similar rights to other employees, I have been treated harshly by British Airways management.

"British Airway can be great again, but it needs to treat Chrstians fairly. I am not ashamed of my faith."

Miss Eweida is suing BA under the Employment Equality (Religion or Belief) Regulations 2003.

Her case is being supported by her union, the TGWU, and she has hired Paul Diamond, a barrister specialising in religious affairs and an adviser for the Keep Sunday Special campaign, to represent her at her employment tribunal.

And a petition of support has been signed by more than 200 fellow workers.

BA is already at the centre of a criminal investigation into alleged price-fixing - which has led to the resignations of two executives.

The airline has come under fire in the past for its adherence to political correctness.

A decade ago it attempted to ditch its traditional Union Flag tailfin in favour of an ethnic design - which provoked the anger of Baroness Thatcher.

Mr Cable, MP for Twickenham and Liberal Democrat deputy leader said: "It is 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.

"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?"

Dr Patrick Sookhdeo, international director of the Christian charity the Barnabas Fund, said: "Discrimination against Christians is commonplace in Muslim-majority contexts, such as Egypt where Nadia's family roots are. "Now we see the same thing increasingly happening within the UK.

"Her Sikh and Muslim colleagues at BA can show their faith publicly in what they wear, but Nadia and other Christians cannot. All we are asking for is a level playing field for all faiths."

Andrea Williams of the Lawyers' Christian Fellowship said: "The forces of political correctness are such that an individual needs to be very determined to protect their rights."