About a million railway employees participated in the strike ballot of NFIR. In December, 800,000 employees participated in the strike ballot conducted by another leading union, the All India Railwaymen Federation, with 96 per cent voting in favour of a strike.
Indian Railways employs about 14 lakh people across India and cross membership widely exists in the Railway unions.
NFIR and AIRF are threatening to go on strike if their charter of demands, which includes the merger of dearness allowance with pay and removing anomalies arising from the 6th Pay Commission, are not met.
"We are writing to the prime minister, Ministry of Labour, Ministry of Finance and the Railways to address our demands before the coming vote on account in February," said a spokesperson of the NFIR.
The unions had earlier threatened a strike last year but it was averred after the Seventh Pay Commission was announced in September this year.