Virgin said: "As a result of the Sky basics issue and also continuing pressure on telephony, we expect negative customer, TV and telephony net additions in the second quarter."
In the first quarter the number of new customers joining was down from 213,500 in October - December to 184,300 between January and March. Monthly churn was 1.6%, down from 1.7% in the previous quarter, though the company said it was too early to see the effect on churn of the loss of Sky's basic channels.
The company earned revenues from its consumer cable operations of £637.3m in the first quarter, up slightly year-on-year from £636.7m.
However, decreasing revenues from the business cable, mobile and content sides of its business mean its profitability has deteriorated.
It made an operating loss of £15.3m in the first quarter, compared with an operating loss of £900,000 in the first quarter of 2006 and an operating profit of £9.2m in the last quarter of 2006.
Profits were depressed by the £25m it spent during the quarter on marketing, which included its rebranding from NTL/Telewest to Virgin Media.
Due to its levels of debt, its net loss for the quarter was £120.3m compared with a net loss of £119.9m in the first quarter of 2006.
Average revenue generated per user was down slightly from £42.82 to £42.75.
The number of customers taking the recently launched V+ HDTV PVR box is now 150,000.
Virgin has started a High Court battle with Sky, accusing it of anti-competitive behaviour.
The cable company is replacing Hollywood icon Uma Thurman with comedienne Ruby Wax for its new branding push.