The international engineering giant has been quoted in the Birmingham Post calling for McAslan's New Street Station scheme to be scrapped amid claims that the station would be running at above capacity just 12 years after completion.
The firm has claimed that the eastern approach to New Street, which bottlenecks 12 tracks into four, means that the station will be running over capacity by 2025.
A Network Rail spokeswoman said: 'We remain committed to the Gateway scheme and it is also backed by Advantage West Midlands, Birmingham City Council and Centro.
'The problem at the station now is the small concourse that is unable to cope with increasing passenger numbers. The Department for Transport's projections of passenger growth are robust and we think they are better positioned to judge this than Arup.
'The proposed plans we have for Birmingham New Street, we believe, will cater for up to a 150 per cent increase in numbers.'
She added: 'The other benefits are that Birmingham New Street is in a central location in Birmingham and the plans are estimated to be a third of the cost of Arup's Grand Central scheme.'