British diplomats secretly discussed granting visa-free travel to the UK for more than 1m Turks, according to leaked diplomatic cables seen by The Sunday Times.

The cache of five documents also suggests that EU officials are attempting to keep any visa deal with Turkey under wraps until after the referendum on June 23.

According to the telegrams, senior diplomats have advised ministers that the proposed EU deal with Turkey on visa-free travel within the Schengen area could lead the UK to consider extending the same privilege to up to 1.5m “special passport holders” from Turkey.

“Visa travel [to the UK] for Turkish special passport holders . . . would be a risk, but a significant and symbolic gesture to Turkey,” wrote Janet Douglas, the deputy