LONDON (Reuters) - Transport for London, controlled by London Mayor Boris Johnson, has bought out the shareholders of subway contractor Tube Lines for 310 million pounds, ending a tumultuous public-private partnership.

TfL said it had bought Tube Lines’ entire share capital and loan notes from owners Amey, a unit of Spain’s Ferrovial, and U.S.-based Bechtel.

As a result of the deal -- which effectively brings the London Underground back under state control and ends months of wrangling over upgrade works -- TfL will take control of maintenance on the busy Jubilee, Northern and Piccadilly Lines from next month.

The deal is due to complete by the end of June.

Johnson was quoted by newspapers as saying the deal freed London Underground and private contractors from “the perverse pressures of the Byzantine PPP structure.”

Bob Crow, general secretary of transport workers’ union RMT, said the buyout was a “recognition on a massive scale that transport privatization does not work” and said RMT would continue to campaign for the renationalisation of Britain’s rail network.