A band of vocal shareholders will this week step up a campaign against a string of Wall Street banks, accusing them of failing to prevent their mortgage-related losses and threatening to vote against several directors at upcoming shareholder meetings.

Union-backed CtW Investment Group, whose affiliated pension funds have over $200bn (£99.5bn) under management, is expected to launch its first attack on Morgan Stanley, and follow up with campaigns against some of the banks with the largest subprime-related writedowns, including Citigroup, Merrill Lynch, Bank of America, Washington Mutual and Wachovia.