Transport Secretary Justine Greening could be hauled before MPs on Monday to explain the UK Government's controversial decision to hand the £5.5 billion contract to run the West Coast Mainline to Scottish-based FirstGroup rather than keep it in the hands of Sir Richard Branson's Virgin Rail.

Tim Farron MP, the Liberal Democrat president, has asked for an urgent parliamentary statement from the Coalition, saying making such a major announcement during the summer recess "makes a mockery of Parliament".

Labour, which wanted the contract delayed so MPs could scrutinise the details, is supporting his request.

"I have written to the Speaker today to ask him to use his power to bring the Government to Parliament to explain their decision and allow us to debate this issue," said Mr Farron. "Announcing the franchise decision in the recess makes a mockery of Parliament."

Mr Farron said he had been inundated by constituents expressing concern at the decision to opt for FirstGroup and that he wanted to "represent their concerns loudly and clearly to the Government".

Meanwhile, the legal wrangling between Virgin Rail and FirstGroup continues. Sir Richard's company is seeking a judicial review of the Government's decision to award the contract to FirstGroup.

The Aberdeen-based company insists it won the contract "fair and square", adding: "We are not about to respond in public for the benefit of the loser."