John Thain, chief executive of Merrill Lynch, has refused to endorse the optimistic view offered by other Wall Street chiefs that the worst impact from the credit squeeze has passed.

“I hope those who say we are at the end are correct. I am somewhat more sceptical,” Mr Thain said Thursday, following Merrill’s disclosure of a $1.97bn first-quarter loss and $4.5bn in additional writedowns on the value of its mortgage-related assets, leveraged loans and other holdings.