A decision over which company will operate the HS2 franchise has been delayed amid concerns with the project and bidders suffering upheaval.
Transport Secretary Chris Grayling said in April that the new franchise - known as the West Coast Partnership - was due to be awarded in June but no announcement has been made.
It is due to begin March 2020.
The outgoing InterCity West Coast franchise has been operated by Virgin Trains since its inception in 1997, running services between London and Glasgow via the West Midlands and North West.
The West Coast Partnership will combine this contract with the new HS2 route, the first phase of which is due to begin services between Birmingham and London from 2026.
A joint bid by Virgin Group, Stagecoach and French state-owned operator SNCF was disqualified by the Department for Transport in April due to a row over pensions.
The trio responded by launching legal action against the DfT in May.
FirstGroup and a consortium led by Hong Kong's MTR are the only other shortlisted bidders vying for the West Coast Partnership tender.
Keith Williams, the head of a Government-commissioned review into the railways, announced earlier this year that franchising "cannot continue" as it is "no longer delivering clear benefits".
Tory Prime Minister hopeful Boris Johnson also announced last month that HS2's former chairman Douglas Oakervee had been recruited to lead a review of the line.
In a written statement to Parliament in April, Mr Grayling said: "We are due to award the West Coast Partnership in June."
A DfT spokeswoman said documents providing information to West Coast Partnership bidders in March 2018 stated that the franchise would be awarded between May and September 2019.
Phase one of HS2 is planned to run between London, Solihull and Birmingham city centre from 2026 while a second phase servicing the East Midlands, North West and Yorkshire is due to begin operations in 2033.
