Porto have referred Chelsea to the buyout clause in Alex Telles' contract.

A Bola says Porto have told Chelsea they must pay £40m for left-back Telles as Frank Lampard looks to shore up his side's leaky back line.

The 27-year-old Brazilian has been a key target for the Blues, who have made several attempts to sign him from the Portuguese club.

But they will need to trigger his £40m release clause that Porto officials are sticking to.

It comes as defender Marcos Alonso is rumoured to be looking for a route back to Italy with Inter Milan.