COLOMBO, Jan 31 (Reuters) - Sri Lanka's key inflation rate in January accelerated to 6.4% from 4% in December, the statistics department said on Wednesday as prices were driven upwards by bad weather and a tax increase.

The Colombo Consumer Price Index, a leading indicator for broader national prices, tracks inflation in Colombo, Sri Lanka's biggest city. (Reporting by Uditha Jayasinghe; Editing by Andrew Heavens)