US investors in Vodafone are being targeted by rebel shareholders who want to force the mobile phone company to spin off its US business and increase its debts to return more cash to investors.

With Vodafone's annual meeting set for next Tuesday, the activist shareholder Efficient Capital Structures (ECS) has welcomed backing from American investor group Glass Lewis for its proposals. About 30% of Vodafone shares are US-held and ECS - backed by former Marconi executive John Mayo and Glenn Cooper, the City banker who floated Manchester United - has been focusing on investors in America to back its four resolutions.

Glass Lewis, which advises 80% of US funds, has recommended that Vodafone shareholders support all but one of those - rejecting ECS's suggestion that any deal over £1bn requireshareholder approval. The group has also advised investors to reject Vodafone's remuneration report.

Raising the prospect of a fresh row over directors' pay, Glass Lewis tells investors it has "severe reservations" about approving the company's remuneration policy.

At last year's annual meeting, investors expressed their anger at a decision to relax targets on the executive bonus scheme, with more than 20% who voted refusing to support the policy. For this year, Glass Lewis flagged up the company's move to soften performance targets once again and raised concerns it may "signal that the remuneration committee will now allow executives to be excessively rewarded for less-than-superior performance".

ECS, wants the company to release up to £38bn by handing its 45% stake in American joint venture Verizon Wireless back to shareholders and increasing its