Emirates, the Middle East's largest airline, faced fierce criticism in Taiwan Wednesday after it reportedly banned cabin crew from wearing the island's flag on their uniforms due to pressure from China.

Taiwan's Ministry of Foreign Affairs said it had lodged protests with Emirates in both Dubai and Taipei.

The airline's cabin crew traditionally wear the flag pin of their own country on their uniforms. 

But a leaked internal email, apparently from an Emirates manager and circulated by local media, ordered Taiwanese Emirates staff to replace the island's flag pin with a Chinese one.

"We have been instructed by the Chinese Government that with immediate effect, Emirates airline cabin crew are to follow the One China policy," the email read.

China still sees self-ruling Taiwan as part of its territory waiting to be reunified. Tensions have rapidly worsened since Beijing-sceptic Taiwanese president Tsai Ing-wen took office last year.

Beijing has stopped all official communication with Taipei, increased military drills and sought to isolate the island internationally.

Beijing says Taiwan is part of "one China", but Tsai refuses to acknowledge that concept. 

Her Beijing-friendly predecessor Ma Ying-jeou recognised the policy, which led to an unprecedented cross-strait rapprochement.

The foreign ministry said it "cannot accept" Emirates' decision. "China is sparing no effort to suppress us on the international stage," it added. 

Taiwanese Emirates workers were outraged by the move.

"My initial reaction was shock, indignation, and anger," an employee at the airline told news website Taiwan Sentinel. 

Apple Daily cited an unnamed staff member who believed the decision was made because Emirates was seeking to add more Asia routes, especially in China. 

Angry social media users took to Emirates' Facebook page, flooding it with the Taiwanese flag in the comment section. 

"Taiwan is Taiwan! How dare you force them to wear another (country's) flag. I along with many Taiwanese will never ride with this airline," one comment said.

The Taoyuan Flight Attendants Union said Wednesday it hoped Emirates would "respect the national identity of crew members from different countries and should not take a coercive or threatening approach".

According to Apple Daily, Taiwanese cabin crew on China flights were also requested to write "Chinese" as their nationality rather than "Taiwanese".

Emirates later apologised in a follow-up internal message, asking Taiwanese crew to "refrain" from wearing their flag pins until further notice, the report said. 

The airline made no immediate comment when contacted by AFP.

Emirates was also criticised last year when it asked Hong Kong cabin crew to wear the Chinese national flag as well as the semi-autonomous city's own emblem.