David Cameron has condemned the ban on England's footballers wearing poppies on their kit as "outrageous".
The Prime Minister called for the sport's ruling body, Fifa, to reverse the "absurd" decision that is stopping the team having the remembrance symbol embroidered on their shirts for this Saturday's match.
He stepped in amid growing fury after it emerged that officials turned down the special request, made by the FA, claiming it would "open the door to similar initiatives" across the world.
Mr Cameron said: "This seems outrageous. The idea that wearing a poppy to remember those who have given their lives for our freedom is a political act is absurd.
"Wearing a poppy is an act of huge respect and national pride. I hope Fifa will reconsider."
The England team are being allowed to wear poppies on their training kit at Wembley on Friday and pay their respects to the war dead with a two-minute silence.
But Fifa has issued a "final statement" rejecting the FA bid for Saturday's friendly against Spain, claiming it would "jeopardise the neutrality of football".
In a letter to the FA, it said: "We regret to inform you that accepting such initiatives would open the door to similar initiatives from all over the world, jeopardising the neutrality of football.
"Therefore, we confirm herewith that the suggested embroidery on the match shirt cannot be authorised. There are a variety of options where the FA can continue supporting the cause of remembrance. One of them already was approved by Fifa, the period of silence."
Jim Boyce, Britain's Fifa vice-president, dismissed claims that the symbol would cause offence. He said: "Personally, I think there has to be a bit of common sense used when requests like this come in. Armistice Day is a very important day in the FA calendar, as it is with other associations, and I don't think it would offend anybody to have a poppy on the shirts."