LONDON, Sept 20 (Reuters) - Britain is to launch a major review of its much-criticised railways after months of disruption to passengers caused by strikes, timetable changes and problems with the franchising system first introduced in the 1990s.

The “root and branch” review will be headed by Keith Williams, a former British Airways chief executive and current deputy chairman of the John Lewis Partnership, the transport department announced on Thursday.

Implementation of any reforms it recommends will start from 2020.

“The review – the most significant since privatisation – will consider ambitious recommendations for reform to ensure our vital rail system continues to benefit passengers and support a stronger, fairer economy,” Transport Secretary Chris Grayling said in a statement.

Williams and his panel will consider all parts of the rail industry, from the franchising system and industry structures, accountability, and value for money for passengers and taxpayers.

They will look at changing travel and work patterns, the department said, and will make recommendations to improve the current franchising model.

Britain’s rail industry was privatised in 1997 under the Conservative government of John Major which separated the running of trains and tracks, but passengers’ groups have long claimed the division promotes buck-passing and inefficiency.

Since privatisation, fares have risen relentlessly and passenger numbers have doubled, leading to overcrowding and putting more pressure on state-owned Network Rail, the organisation that maintains tracks and upgrades infrastructure.

Services on several lines have been further hit by strikes as unions try to protect the role of guards on trains and by chaos caused by timetable changes introduced by eight franchises in May which led to widespread delays and cancellations.

Also in May, the government was forced to renationalise the rail route between London and Edinburgh for the third time since 2007 after the private company over-estimated profits, reigniting the debate over who should run the railways.

Unions have long called for the rail system to be re-nationalised but Thursday’s announcement of the review made no mention of any change to the current franchising system.

“Privatisation has led to a level of growth never seen under nationalisation, and reversed the decline the railways saw under British Rail, where routes and stations were closing,” the department said in its statement.

“The government has already taken steps to strengthen future train franchises and improve reliability. However, we want to ensure the rail system continues to deliver benefits in the face of these challenges,” it added. (Reporting by Stephen Addison; Editing by Alistair Smout)