London Ambulance Service trust finished the past financial year with a £1m deficit and a net deficit of £587,000 after previous surpluses were taken into account.
Its annual report admits this is 'right at the limit of the cumulative deficit permitted'.
The service is now taking up to 3,000 emergency calls a day. It responded to 704,425 emergency calls in 1999-2000 - up from 684,988 the previous year.
Writing in the annual report, new chief executive Peter Bradley says staff worked 'harder than ever' but 'struggled unsuccessfully' to reach performance targets.
Just 84 per cent of emergencies were reached within 14 minutes and 34 per cent in eight minutes.
This year, LAS has a target of reaching 45 per cent of 'category A' calls in eight minutes and 90 per cent in 14 minutes.
The trust is implementing a computerised priority dispatch system, putting more resources into busy periods and using paramedics to give telephone advice to some 999 callers.
An additional£6m secured for this year will be used to buy more fast-response motorcycles and recruit an additional 125 staff.
But Mr Bradley says that the LAS is now 'at a crossroads' and needs to unite around an improvement programme developed earlier this year.
Chair Sigurd Reinton says the resource level for the LAS 'must be reset' to take account of demand, frontline crews must get 'better leadership' and demand must be managed 'more proactively.'
London Ambulance Service trust annual report 19992000. www.lond-amb.sthames.nhs.uk