* Considering proposal to cut 300 roles

* Roles to be affected- retail and digital

* Total headcount of 8,200

Nov 2 (Reuters) - Thames Water, Britain's biggest water supplier, is considering a proposal to axe around 300 job roles, of which over half are currently vacant, a company spokesperson told Reuters on Thursday.

The company is trying to emerge from a tumultuous year, in which it faced possible nationalisation at one point, through a range of cost reduction measures.

Weighed down by 14 billion pounds ($17.07 billion) of debt and under pressure over sewage releases into British rivers and seas, Thames Water avoided a government rescue in July when investors agreed to inject 750 million pounds into the company.

"The last year has been an extremely challenging year for the business and we continue to take a rigorous approach to financial discipline throughout the company in order to operate within budget," the spokesperson said in an emailed response.

The proposed changes will risk roles primarily from Retail and Digital functions and are unlikely to impact front line employees.

The spokesperson added that the company will seek to minimise compulsory redundancies wherever possible.

The company informed it has consulted unions- GMB, Unite and Unison before the announcement.

Thames Water currently employs about 8,200 people across its business.

($1 = 0.8201 pounds) (Reporting by Anchal Rana in Bengaluru; Editing by Maju Samuel and Alistair Bell)