First time home buyers could be thrown a lifeline under plans being considered by the Treasury to underwrite 'risky' mortgages, allowing people with only small deposits to buy homes.

Since the credit crunch took hold, banks have demanded far tougher criteria for lending, asking buyers to provide between 25% and 30% of the price of a home as a deposit.

There were 30,000 loans to first time buyers in the first three months of 2009 against an average of more than 100,000 a quarter in the previous decade.

But the government is now studying a scheme used in Canada in the hope of encouraging banks and building societies to step up their lending. The Canadian programme requires all mortgages secured with a deposit of 20% or less to be insured by the government or private insurers, giving the banks more confidence to lend.

The Treasury has taken soundings from specialist insurance companies such as Genworth Financial, which suggest that the Canadian housing market has withstood the pressures of the global financial crisis better than most.

If the Treasury copied the scheme it might have to act as the insurer in the first instance before stepping back to underwrite insurance from private sector companies – opening the government to considerable criticism as it would put further taxpayer money at risk at a time when public finances are already stretched.

The amount of money flowing in the financial system still remains a concern for the government despite attempts to encourage lending through bank bailouts. Chancellor Alistair Darling is tomorrow scheduled to call in the major lenders to urge them to step up their lending to homeowners and small businesses to help stimulate the economy which has now contracted for five quarters in a row.

The possibility of the insurance scheme is outlined in the white paper on banking reform published this month and the Treasury promises an up-date in the autumn's prebudget report. "Some countries have adopted alternative models for mortgage insurance such as Canada where mortgage insurance is compulsory for all mortgages above a lower limit and below a maximum proportion of a home's value," the paper said.

"Some UK stakeholders have proposed that the government considers the benefits of international models like Canada. The government is interested in the lessons that may be learnt from the experiences of other countries and will update at the pre-budget report," the paper said.

The Treasury has made no decision on whether it would work here. The paper explains why it is being considered. "It is sometimes argued that this model helps provide borrowers with continued access to mortgage finance by encouraging risk sharing between insurers and lenders, and helping ensure that lenders do not take excessive risks when the economy is growing and do not withdraw from higher LTV lending during periods of economic disruption," the paper said.

But Treasury officials are also mindful of the pitfalls of the scheme which can push up the price of loans to first time buyers and others with small deposits. It might also be accused of trying to promote risky lending again or breath life into mortgage indemnity guarantees which lenders have charged customers for high loan to value loans but were largely scrapped in the mid 1990s.

The idea is being pushed by specialist insurers who might sell the necessary insurance to the banks. Genworth Financial, a US-based company, is among those to have submitted proposals. It is suggesting that the state would act as direct guarantor initially and that private sector players would step in to allow the government to "reduce its role from being a direct insurer to a guarantor of the private mortgage insurance providers".

"We urge the government to consider developing a partnership with mortgage insurance providers in order to prudently and efficiently provide a lasting and sustainable solution to prudently and efficiently provide a lasting and sustainable solution for the wholesale mortgage market," Genworth said.