Campaigners made their feelings clear at drop-in events.
Four-platform rail link on Cambridge Biomedical Campus expects to handle 1.8m passengers a year.
But East West Railway Co admits northern route would be cheaper and less environmentally damaging
It calculates that 300 buses per hour would be needed under GCP plans - but says phase one of light rail could be delivered for £600m.
The government has also announced funding relating to growth around new stations.
More homes than currently exist in the whole of Cambridge could be built in the area by 2041 under a revised housing blueprint put forward.
There is still uncertainty over the final route.
A new £184million Cambridge South railway station will be built after plans were approved by the Department for Transport.
There had been doubts over the Bedford-Cambridge section.
Campaigners brought a white elephant to the event.
Residents are reminded that a face-to-face meeting with representatives from East West Rail is set to take place today (Wednesday, October 12).
Buses alone ‘not the full answer for city’ says Cllr Lucy Nethsingha.
The PM said that not building these projects fast enough was ‘one of these reasons for our sluggish economic growth’.
Peter Blake’s comments will fuel further speculation over the future of the £5bn scheme.