A report by the Commons Transport Select Committee found policy changes imposed by the Coalition Government had played a role in the flawed bidding process for the route, but were compounded by shortcomings at the Department for Transport.
The MPs have now called for clarity on the cost to taxpayers of cancelling the competition, which resulted in £40 million being repaid to the four bidding companies.
A report last month, commissioned by the Government, gave a damning indictment of how the competition was handled, though a second report this month found the system could be reformed.
Committee chair Louise Ellman MP said: "Ministers approved a complex franchising policy at the same time as overseeing major cuts to the Department's resources. This was a recipe for failure which the DfT must learn from urgently."