Manchester United fans angry at their recent takeover by Malcolm Glazer have been urging shirt sponsor Vodafone to "hang up" on the US tycoon.
Vodafone signed a four-year deal with Man Utd in late 2003
Fans have been calling for a boycott of major club sponsors, such as Vodafone.
"The tie-up with Malcolm Glazer is bound to reflect negatively on the company," said campaign group Shareholders United.
But Vodafone said it did not see any reason why it should not continue to benefit from Manchester United links.
Outside the mobile firm's AGM on Tuesday fans said Vodafone was at risk of being connected with a "severely tainted brand".
Protesters carried posters saying "Hang up on Malcolm Glazer" as shareholders made their way into the meeting.
But the firm's head of marketing Peter Bamford said the number of contract cancellations in protest at Manchester United was "very, very small".
However, Vodafone has not renewed its sponsorship agreement with ex-United star David Beckham, which was signed in 2002, and renewed in 2004 for a further 12 months.
'Very big issue'
Shareholders United warned that Vodafone's public image may suffer if Mr Glazer's stewardship of the club was not successful.
In December 2003 Vodafone and Manchester United signed a £36m four-year shirt sponsorship deal.
"If Manchester United does fail financially, as many think it will, it will be the biggest failure football or sport has ever seen. Vodafone will be tied in with that," said Nick Towle, of Shareholders United/Manchester United Supporters Trust.
"This could be a very, very big issue for Vodafone."
He said with so many fans unhappy with Mr Glazer's takeover it is likely that many will cancel their Vodafone contracts.
They may also be "reluctant" to buy Vodafone's Manchester United Mobile products and services, a key aspect of the strategic tie-up between the two companies, Mr Towle added.
"Sponsorship is supposed to enhance a brand, not endanger it," he said.
Supporters who are unhappy at Mr Glazer's £790m buy-out have vowed to boycott Manchester United matches and products, and any products or services associated with the club.
As well as Vodafone, boycotts could also potentially affect sales at Nike, Pepsi and Budweiser.
Those opposed to the Glazer deal have protested at the level of debt used in the takeover.
The Glazer family has had to seek £540m of borrowing, including a £265m loan facility secured against United's assets. Mr Glazer's plans for the club are reported to include raising its revenues by 52% by 2010.
Vodafone said on Monday it had added a net 4.1 million new users in its first quarter to 30 June, ahead of forecasts and up 35% on a year ago.
Global subscribers now totalled 165 million, boosted by growing markets such as Spain, Italy and Romania.
Vodafone signed up 1.1 million new 3G users in the quarter, taking total registered 3G users to 3.3 million.