In the absence of the ambassador, the ministry summoned the charge d'affaires "to express our concerns over the allegations,” a foreign ministry diplomat said on condition of anonymity, adding that Ankara was expecting an "official and satisfying explanation" from British authorities.
The claims, reported by the Guardian newspaper, are that GCHQ - Britain's electronic eavesdropping agency - spied on foreign politicians and officials attending two G20 summit meetings in April and September 2009.
UK intelligence agencies were said to have set up internet cafes specifically to enable them to read the emails of those taking part in the summit, the paper quoted the leaked documents as saying.
It alleged that the operation was sanctioned at a senior level in the government of then prime minister Gordon Brown and the intelligence obtained was passed to ministers.
The Turkish finance minister and South African delegates are said to have been among those targeted.
In a statement, Turkey's Ministry of Foreign Affairs said: "The claims published in today's edition of the Guardian that phone conversations of our Minister of Finance Mehmet Simsek and his delegation were tapped during their visit to the United Kingdom in 2009, on the occasion of the G20 meeting, are alarming.