Underwriters to the HBOS rights issue were preparing yesterday night to pick up the tab for the UK mortgage bank’s £4bn cash call after a fresh slump in the stock made it highly likely that shareholders would shun the fundraising. HBOS shares fell as much as 13.5% in morning trade, and closed down 2% at 254.5p, 7.5 per cent below the 275p subscription price. Investors have until Friday morning to take up their rights. If the underwriters are forced buy the shares, it will be the highest profile offering to fail since the stock market crash of October 1987. As much as half of the issue might have been sold to sub-underwriters, bankers said, leaving Morgan Stanley and Dresdner Kleinwort, the lead underwriters, on the hook for about £1bn each. People close to HBOS stressed that the bank would receive £4bn in cash regardless of the outcome of the rights issue, and defended the decision to boost its capital reserves.