Turkey’s central bank burnt through almost $12bn defending the lira in a record intervention after President Recep Tayyip Erdo?an’s detention of his political rival triggered a political crisis that scared investors and sent the currency reeling.

The bank spent $11.5bn propping up the currency on Wednesday after the detention of Istanbul’s mayor, Ekrem ?mamo?lu, the most prominent leader in Turkey’s political opposition, said a person with knowledge of the matter and calculations based on official data by Bürümcek?i Research and Consultancy.

The intervention was nearly four times larger than any previous such move on the bank’s official records. It came after the lira plunged as much as 11 per cent against the US dollar to a record low on Wednesday as Erdo?an’s move against ?mamo?lu ignited a stampede out of Turkey’s markets.