Mr Fischer, a train expert, has joined Nationals candidate for the Polwarth byelection David O'Brien to spruik for better train services in Victoria's west.

The former Nationals Leader says a there is a "bottleneck" in the $3.65 billion Regional Rail Link, at a critical intersection where trains from Geelong and Ballarat converge at Deer Park West.

Mr Fischer said a junction was built instead of a flyover to save money, which has forced trains to travel at 65 km/h.

And due to congestion, trains sometime have to wait for five minutes for the track to be clear, he said.

"Nobody builds major commuter junctions anywhere in the world without grade separation. It has now become choke-point Charlie."

"There was federal funding for that rail overpass and that money went back to Canberra."

May's state budget showed a $450 million cut in the final cost of the link, from $4.1 billion to $3.65 billion and the federal budget papers later revealed that $187 million of Commonwealth funds had been reallocated to duplicating two rural highways.

Mr O'Brien is attempting to win the seat of Polwarth, which the Liberals hold by 10.6 per cent – it has been made vacant by the retirement of Terry Mulder, a former transport minister.

As part of his push Mr O'Brien is calling for a trial of shuttle train services between Geelong and Warrnambool when major events are held in the district, such as Warrnambool racing carnival in May.

Mr O'Brien believes the public would use the shuttle and Mr Fischer backed the call, citing the success of special train services to the Clunes Book Festival.

Transport Minister Jacinta Allan said the former Napthine government had spent a year reviewing the Regional Rail Link and decided not to include a flyover at Deer Park.

She also said the former government had not delivered any extra services on the Warrnambool line.

"The Nationals, when in government with the Liberals, couldn't deliver a single extra weekday service for Warrnambool in their four years, despite the Warrnambool line travelling through both the then premier's electorate and the then public transport minister's electorate," Ms Allan said.