UK rail unions have launched a legal challenge over the way the government plans to award three rail franchises.

The Rail, Maritime and Transport (RMT) union, Aslef and the Transport Salaried Staffs Association (TSSA) are calling for a judicial review into the reprivatisation of the East Coast line, and the extensions to the Thameslink and Great Northern awards.

The unions argued that their members' jobs and conditions were threatened by a lack of consultation and accused the government of rushing the process.

"After the scandal of this government robbing the British taxpayer of a billion pounds in the scramble to privatise the Royal Mail it is shocking that they are engaging in the same tactics to try and hand the East Coast Mainline back to their friends in big business," said Mick Cash, the acting general secretary of the RMT.

The move comes ahead of the East Coast franchise being complemented before the 2015 General Election.

"The coalition knows only too well that rail franchising is not fit for purpose," said Manuel Cortes, leader of the TSSA.

"Rail workers are at a loss to understand why the government insists on going forward with a broken system which threatens the interests of passengers and taxpayers."

A Department for Transport spokesperson said: "We will vigorously defend this claim and remain committed to the franchising programme.

"As these legal proceedings are ongoing it would not be appropriate to comment further at this stage."