Calls for desalination plants and more reservoirs have come from the consumer watchdog for water after further Environment Agency drought warnings.
Water firms are hoping for more rain for winter and spring
The Consumer Council for Water (CCW) also called on firms to address leaks.
Southern Water, which has said it is facing the worst drought in nearly 100 years, said new resources need planning permission and government approval.
The firm said it was meeting targets in reducing water lost from the company's and privately-owned leaking pipes.
Figures from the Met Office show that Kent and Sussex had less than a third of the average monthly rainfall in January.
And the region has also had below-average rainfall for 12 of the last 14 months, making 2005 the fourth driest year since 1921.
The CCW said: "Water companies need to address leakage and additional resources are needed, be it through new reservoirs, desalination plants or making the best of what we have by improving connections between supply networks in the South East."
It found "a dangerous mix" in the South East region of high levels of demand and development, coupled with limited supplies.
Standpipes 'long way off'
Southern Water - one of several companies supplying customers in the region - said it was "important to remember the conditions we are currently experiencing are exceptional".
On Tuesday, the Environment Agency warned that water-saving measures could continue into the summer. Hosepipe bans brought in last summer are still in place.
Southern Water has said it is a "long way off" measures such as introducing standpipes - a measure seen in some parts of the UK during the 1976 drought.
Last week, the Environment Agency granted the firm a drought permit allowing it to take more water from the river Medway, after Bewl Water reservoir in Kent reached its lowest level since it was built in the 1970s.