Manchester United’s frantic search for defensive reinforcements has encountered fresh turmoil amid a legal dispute over the ownership of Marcos Rojo.

Having seen United miss out on several leading transfer targets, Louis van Gaal identified Rojo, the Sporting Lisbon and Argentina defender, as a priority as the club prepare to kick off the new Barclays Premier League season at home to Swansea City tomorrow. United have made a £16 million bid but have been left frustrated by a row between Sporting and the investment fund that owns 75 per cent of Rojo’s economic rights.

In addition to claiming that Doyen Sports had conducted unauthorised negotiations with other clubs, a Sporting statement also accused Nelio Lucas, the chief executive, of threatening last summer that Rojo would