Daily rail journeys have dropped to an average of 55% of pre-covid levels across the UK, according to figures from the Department for Transport (DfT).
The number of people using rail to travel has continued to drop since Omicron was first reported by South Africa on November 24, 2021.
December 13 saw the introduction of work from home guidance in England, with many fewer people travelling.
This led to a further drop in rail industry revenue, down by 23% week on week.
Industry body, The Rail Delivery Group, said this means income from fares is now at the lowest level since the end of July, when the country first reopened after lockdown.
In the Spending Review, the Government committed a further £5.7 billion over three years from 2022 to keep essential rail services running.
This is in addition to over £15bn committed so far during the pandemic.
Andy Bagnall, director general at the Rail Delivery Group, said: “Like many other parts of the economy, Omicron is dealing another blow to the rail industry, which has seen its finances decimated by the pandemic.
“The railway cannot take more than its fair share of support from the taxpayer which means changing to be more sustainable and more customer focussed.
“That will allow the railway to build back stronger for the country as we emerge from the pandemic.”