US Senators from both sides of politics are calling for an urgent vote on the country’s flood insurance program, which is due to expire in May.

The National Flood Insurance Program (NFIP) is the only underwriter of flood insurance policies in the US, and its funding effectively expired in 2008.

A series of short-term extensions has kept it going, but there were four gaps in coverage in 2010, totalling 53 days, and there are concerns that there could be another lapse if the Senate fails to debate and vote on the NFIP, which is part of a broad-ranging new tax bill.

The Republican-led House of Representatives passed the new bill, the Middle Class Tax Relief and Job Creation Act, last December. But it is linked to the approval of the $US7 billion ($6.49 billion) Keystone XL Oil Pipeline project, which President Barack Obama rejected in January.

The bill includes proposed reforms which would provide both a stable five years of flood coverage and authorise the Federal Emergency Management Agency to reinsure parts of the NFIP in the private reinsurance markets.

A bipartisan group of 41 Democrat and Republican senators has written to Senate leaders asking them to schedule a vote on legislation.

The letter asks for “long-term re-authorisation and meaningful reform of the NFIP as expeditiously as possible in February or very soon thereafter”.

The flood insurance program covers about 5.6 million property owners across the US who pay subsidised premiums for their policies.

However, the program is about $US18 billion ($16.7 billion) in debt because of the large claims associated with Hurricanes Katrina and Rita in 2005.