Three rail unions are launching a legal challenge to put the brakes on the coalition privatisation of East Coast Main Line, Britain’s only publicly-owned inter-city rail service.

RMT, Aslef and the TSSA are seeking a judicial review over any sale of the line, which links London Kings Cross with Edinburgh via centres such as Peterborough, Doncaster and Leeds.

The service was privatised in 1996 but taken back into public ownership in 2009 when incompetent contractors National Express Group proved incapable of operating it efficiently despite receiving millions in taxpayer subsidies.