Network Rail said any plans for the line must go through formal consultations
Campaigners fighting to improve local railway services lobbied Network Rail bosses when they met to discuss future transport plans for Bristol.
Network Rail (NR) propose the minimum service needed on the Severn Beach line is hourly.
Friends of Suburban Bristol Railways (FOSBR) disputes this, claiming NR has used 2007 figures which do not show increases in passengers since then.
FOSBR will also meet local councillors and MPs to discuss the issues.
The group claims Network Rail has rejected the Greater Bristol Metro project which would offer a half-hourly service cross-city from Weston to Yate.
The proposal has the support of the West of England Partnership which has included it within its bid for government transport funding.
"People want a good local train service," said Rob Dixon of FOSBR.
"We need to invest in rail schemes like Portishead, the Greater Bristol Metro, doubling the track between Clifton Down and Montpelier and increasing the number of tracks on the mainline."
FOSBR is also calling for the line from Temple Meads to Parkway, which is currently two tracks, to be widened to allow more services to be run.
In a statement Network Rail said: "Network Rail shares the aspiration to grow and improve the railway and welcomes opportunities to achieve that.
"Any proposals have to go through the formal process of consultation with the wider industry, which include train operators and local authorities.
"The wider industry will have to agree the feasibility of the proposals put forward before they are included in the 10-year strategy."