Vietnam’s benchmark VN Index ended down 0.4 per cent on Friday, a one-month low, as investors sold the shares of energy companies following a parliamentary panel’s decision to triple the environment tax on oil products.

A National Assembly committee had approved a Finance Ministry plan on March 10 to triple the environment tax on petrol and most oil products from May 1, the government had said on Wednesday.

The index closed at the session low of 586.10, its lowest since February 12.

Volumes rose 17.6 per cent from Thursday to 97.28 million shares, above the five-day average of 94.07 million shares, based on Thomson Reuters data.

PetroVietnam Gas, the country’s largest listed firm, dropped 1.3 per cent, PV Drilling lost 1.8 per cent and PV Trans dipped 0.7 per cent.