The fact is the banks have to earn a spread from the rate they lend against the rate they borrow, otherwise you get into the Northern Rock position with the cost of borrowing exceeding the return on lending. Politicians will nevertheless huff and puff regardless of reality.
UPDATE : The government is going to force banks to double their holdings of government bonds, supposedly to increase their “liquidity reserves”. Handy when the government is desperate to find buyers for gilts to keep itself afloat. If they have to buy gilts, it will make it even more difficult for banks to extend credit to corporate borrowers… doh!