* BoE says will be vigilant about rise in UK house prices
* Risk of interest rate spikes "at heart" of FPC monitoring
* UK faces extra house price crash scenario in EU bank tests
* Review of leverage ratio will not set actual figure
* Analysts say FPC tone points to more action on housing (Adds analysts' comment)
LONDON, March 27 (Reuters) - The Bank of England urged banks on Thursday to consider the risk of future spikes in interest rates when they approve mortgages, and prepared tools to rein in potentially dangerous lending.
British house prices have risen by around 10 percent over the past year, and the central bank said mortgages were higher as a share of home-buyers' income than at any point since 2005, although other indicators remained weaker than average.
Some commentators argue that parts of Britain's housing market are already in a bubble and the BoE's Financial Policy Committee, which monitors risks to the financial system, said it was keeping a close eye on the sector.
"Given the increasing momentum, the FPC will remain vigilant to emerging vulnerabilities, will continue to monitor conditions closely and will take further proportionate and graduated actions if warranted," the Bank said.
From next month the body that regulates how British banks lend to consumers, the Financial Conduct Authority, will introduce tougher home loan underwriting standards.
The BoE said in a report of a quarterly meeting of its risk watchdog, the Financial Policy Committee, that from June it hoped to have the power to set the interest rate scenarios that lenders would have to consider when granting loans.
The central bank also said that when it conducts its part of European Union-wide stress tests for banks this year, it would also make them consider the risk of a sharp rise in interest rates and a big fall in house prices.
JPMorgan bank said it expects stricter mortgage stress tests for borrowers and lenders as a minimum step by the FPC.
"But a continued rise in transaction levels together with double-digit house price inflation would probably push the FPC into taking further steps," JPMorgan said in a research note.
Banks could be forced to hold more capital against mortgages and there was a "high chance" the FPC will recommend scaling back the second phase of a government scheme to help homebuyers, JPMorgan said.
The FPC made no new formal recommendations, but it said that concern about financial markets' readiness for a rise in interest rates was "now at the heart of the FPC's risk and vulnerability assessments".
The BoE added that British banks' financial health had improved since its last report in November but that uncertainty about the cost of past misconduct had increased.
Banks like Barclays and Royal Bank of Scotland have been fined millions of pounds for rigging the London Interbank Offered Rate, or Libor, an interest rate benchmark.
Lenders are also paying huge sums in compensation for mis-selling loan insurance and allegations are emerging that banks have manipulated the foreign exchange market.
Separately, the Bank published its terms of reference for an assessment of leverage ratios at banks, which it said would report back in November. However it will not set a numerical value for a leverage ratio until later.
The FPC is likely to get power in future to raise leverage ratios at British banks to above international minimum levels.
Under the global accord known as Basel III, banks across the world must hold capital equivalent to at least 3 percent of their total assets on a non risk-weighted basis from the start of 2018. The aim of this so-called leverage ratio is to serve as a backstop to a bank's core capital buffer, which is based on risk-weighted assets.
Policymakers in Britain, Switzerland and the United States have put more emphasis on the leverage ratio, saying banks can too easily game risk-weightings in their core buffers and that a higher ratio is required. Analysts expect them to set higher levels than Basel III.
"We expect the UK regulator will eventually settle on a 4-4.5 percent hurdle rate, to be achieved by end-2017. Barclays looks most at risk," Citi bank said in a research note.
The FPC also said it was minded to require big banks to add up risks on their books using the same standardised model as smaller lenders.
Policymakers have become sceptical about how large lenders use in-house computer models to tot up risks, a calculation which determines how much capital they must hold.
The FPC said banks who use in-house models may have to report figures under the standardised approach as well following a review due in the first half of next year.
"On a standardized basis we estimate Lloyds would see the greatest risk-weighted assets inflation," Citi bank said.