* May overtake 2007 floods for damage with more rain expected
* Aviva, Direct Line, RSA, AXA say too soon for cost estimates
* Many victims would not be covered by 'Flood Re' scheme
By Noor Zainab Hussain and Simon Jessop
LONDON, Dec 29 (Reuters) - Insurers are facing some of the costliest British floods on record as large parts of northern England, already inundated, brace for more heavy rain.
Accountants estimate that insurers are currently facing a bill of up to 1.5 billion pounds ($2.22 billion) after towns, cities and countryside were deluged in recent days in the worst floods in Britain since 2007. However the damage looks set to rise with a storm forecast for Tuesday evening and Wednesday.
"With more storms on the way it could get towards as large as anything that we've had in recent history, certainly in terms of insured loss," said Simon Waller, managing director at JBA Risk Management, which assesses flood risk for companies and governments globally.
Around 6,700 properties have been damaged so far according to the Environment Agency, with accountancy firm KPMG estimating the total economic impact of the floods will be more than 5 billion pounds.
Typical flood insurance claims tend to be around 30,000 pounds though can often run as high as 130,000 pounds, JBA said.
But the outlook for more rain, along with difficulties accessing some of the affected areas, mean most insurers say they cannot yet provide detailed estimates on the scale of the claims they are facing.
Aviva, RSA, AXA and Direct Line , among the insurers facing payouts, said it was still too early to give an idea of the cost given the current weather forecasts.
"The threat of severe flooding this month, particularly in the North and North West, has been continual and shows no signs of abating in the short term," said Amanda Blanc, chief executive of AXA & Ireland General Insurance in a statement.
Floods and storms in 2007, which hit north-east, central and southern England and Wales, cost insurers a total of 3 billion pounds according to the Association of British Insurers.
There are nine severe flood warnings in place in northern England, meaning there is a danger to life, while there are lesser warnings in Scotland, Northern Ireland and Wales due to the forecasts of further rain.
The scale of damage along with the increasing frequency of floods, is casting doubt on the capacity of a government-backed insurance plan to protect against future catastrophes.
Flood Re, a government and industry sponsored insurance vehicle which helps ensure flood cover for high-risk properties, is due to launch in April. But with water now hitting homes and businesses which were either not insured or previously considered less risky by insurers, there is a question about how many of the current floods' victims would have been covered under the scheme.
"I think there will be a lot of political pressure following the floods because there are a number of properties, particularly small businesses that are excluded from Flood Re, who probably are suffering very badly," said JBA's Waller.
Prime Minister David Cameron defended the government's record on flood defences during a visit to York on Monday, where large parts of the historic city are under water. Cameron said it had committed to spend 2.3 billion pounds ($3.4 billion) over the next six years, and he would consider doing more.
But the Environment Agency, which is responsible for handling the response to floods, has said Britain needs a "complete rethink" of its defences as the country moves from "known extremes to unknown extremes" in weather patterns.
Insurers say that as well as improving defences, buildings now need to be constructed to better withstand flood waters.
"It is abundantly clear that creating greater resilience to the impact of floodwaters is as important as prevention if we are to adapt to what increasingly appears to be the new normal," said AXA's Blanc. ($1 = 0.6748 pounds) (Additional reporting by Kate Holton and Carolyn Cohn; editing by Anna Willard)