Brisbane buses will follow trains underground at Roma Street Station as the government forges ahead with Cross River Rail plans, without the federal help it hoped to get from a Shorten Labor government.

A new underground train station had already been promised for the inner-Brisbane transit hub, but deputy Premier Jackie Trad announced on Friday that the bus interchange would also be moved below.

The new Roma Street station will be built where the existing Transit Centre stands.

Ms Trad, who is also Infrastructure Minister, said it would provide a "seamless connection" between rail and bus.

“That means public transport becomes very, very reliable but also very accessible," she said.