The ban on British Airways (BA) employees wearing crosses shows British Christians are being "discriminated against", a Democratic Unionist Party (DUP) MP has warned.
Jeffrey Donaldson said Christians were feeling themselves "increasingly under pressure" and warned ministers must start listening to the "majority in this country who are fed up of being discriminated against".
His comments, made during a session of prime minister's questions, came just days after Tony Blair weighed into the row about whether a BA check-in clerk should be allowed to wear a visible cross on a necklace while at work.
Nadia Eweida, from Twickenham in south-west London, refused to comply with the airline's rule against wearing visible jewellery. She lost her first appeal but has one more chance, and is staying at home on unpaid leave until then.
Her case has prompted outrage from both Church of England archbishops, and more than 100 MPs have signed a motion questioning BA's rules. The airline has defended its decision, but on Friday announced it was reviewing its uniform rules.
In a question and answer session at the Confederation of British Industry (CBI) annual conference on Tuesday, BA chairman Martin Broughton called upon the prime minister to accept the difficulty of his firm's position.
Jack Straw, the leader of the House of Commons, earlier this month said he found BA's position on this issue "quite inexplicable", saying if Muslim women could wear a headscarf, so should Jews be able to wear the star of David and Christians wear a cross.
But Mr Broughton asked Mr Blair: "Given that the police, army and other government uniformed staff have an identical policy to BA in relation to crosses outside uniforms, do you find the government's policy also wholly inexplicable?"
He went on to complain about the "minefield of anti-discrimination legislation" that British firms had to comply with, saying that although people argued allowing Ms Eweida to wear her cross was "commonsense", it was actually illegal under such laws.
However, in response, Mr Blair urged him to give up the fight. He said: "One of the things I learnt in politics is there are battles really, really worth fighting and there are battles really, really not worth fighting.
"All I would say is get the right side of the line on this. I totally understand, it's really difficult and incidentally I think British Airways is a great airline. But there are some things they arise in a certain way and you're best just to do the sensible thing."
Responding to Mr Donaldson's comments in the Commons this lunchtime, deputy prime minister John Prescott - who was standing in for Mr Blair - urged him to show "tolerance", which was, after all, what religion was about.