The former headmaster has claimed that he made the decision to step down from his high ranking position "to pursue new career opportunities" but the highly unexpected move leaves ParalympicsGB looking for a new head just 18 months before the London 2012 Paralympic Games take place.

Lane said: "With 18 months to go to the Games in London, the staff team at ParalympicsGB is well placed to deliver fantastic support to British Paralympic athletes and ensure their continued success.

"I am looking forward to watching them compete in what promises to be the best Paralympic Games ever.

"This exciting time for British sport is providing an ideal environment for me to pursue new career opportunities and build on the experiences I have gained in the last ten years."

Lane, who was Chef de Mission of Great Britain’s Paralympic team at the last four Paralympic Games, led them to second-placed finishes in the medal tables at both Athens 2004 and Beijing 2008 while Paralympic sport in the UK has seen unprecedented growth and profile under his leadership.

A search for a new successor has already begun but is made more difficult by the fact that ParalympicsGB have not yet recruited a chief operating officer following the departure of Tanya Crook.

Crook vacated the position last October to become the head of new sport engagement at the British Olympic Association (BOA), who share their headquarters with ParalympicsGB at Charlotte Street in central London.

Tim Reddish, chairman of ParalympicsGB, said: "Phil has chosen to focus attention on new challenges and I respect that.

"On behalf of myself and the Board, I would like to thank Phil for the work he has done over the last ten years promoting the Paralympic Movement and his significant contribution in successfully taking the ParalympicsGB Teams to the last five Winter and Summer Paralympic Games.

"We wish him all the very best in his future endeavours.

"This is an exciting time for ParalympicsGB and the Paralympic Sport Movement.

"ParalympicsGB will be implementing a recruitment strategy to identify Phil's successor to lead the organisation through to 2016 and beyond."

Lane contributed heavily to the creation of the first multi-sport Paralympic World Cup, which is now the the largest annual international multi-sport competition in elite disability sport, and was awarded an OBE in the 2009 New Year Honours List.

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