The group said the losses were largely due to increased amortisation, depreciation and interest payable after recent acquisitions including Eurobell and Flextech.
Turnover, however, increased by 34% to £321m and revenue per household grew 4% to £38.80.
The cable operator, still slightly behind its larger rival NTL in the race to sign up digital subscribers, said it had added 39,000 overall cable TV customers during the period ending March 31.
Subscriber numbers for its digital cable TV service Active Digital stood at 532,000 on June 4, representing 41% of its total cable TV customer base of 1.3m as it finally made it past the golden 500,000 mark.
Telewest missed this target earlier this year because of supply problems at its then sole set-top box provider Pace Microelectronics. The operator has since rectified this situation with the appointment of US-based set-top manufacturer Scientific Atlanta.
Customer churn rate for cable TV service shrank 2.9% to 23.7% but ARPU (average revenue per user) also fell from £20.83 to £20.08 following price cuts last year.
The operator said it is increasing its monthly subscription fees by an average of £2, although its basic package will go up by just 60p.
Telewest shares were trading at 117.7p at 11.40am this morning. They have improved 19% this year while rival NTL's stock has fallen 13%.