Manchester United fans are mobilising shareholders and supporters to try to block the takeover of the club by US sports tycoon Malcolm Glazer.

Mr Glazer is believed to be the unnamed investor behind a preliminary approach made to United’s plc board.

Supporters group Shareholders United, which owns 1.4% of MUFC, wants to raise the fans’ stake to 10%.

Moreover, a militant wing of Manchester United supporters has already embarked upon aggressive tactics in an attempt to thwart Glazer’s attempt to buy he club.

The house and car of United director, Maurice Watkin, were daubed with red paint on Monday night, in what is believed to be the first act in a concerted campaign to scupper any deal.

A spokesman for the club moved last night to condemn the incident, saying: “Manchester United condemns the acts of vandalism committed against one of its directors, Maurice Watkins, yesterday. The behaviour of a few individuals does nothing to enhance the reputation of the club they claim to support.”

Though Glazer’s assets are valued at £630m, he does not have the resources required to launch a takeover which would cost up to £800m. The worry for fans is that he would he would borrow the money to complete the acquisition and would servcie the loan from club profits.

Meanwhile, Shareholders United launched a media offensive in an effort to discredit a bid from Glazer.

“We have got various plans going forward at the moment,” Nick Towle, chairman of the group, told BBC News Online.

“Fans are aware of the dangers and pitfalls of the club falling into the hands of Mr Glazer or some other individual.

“Mr Glazer would have to take out a number of loans to achieve any takeover, which would turn United from a debt-free club into a debt-laden model.”

The group intends to write to 37,000 small United shareholders, asking them to join Shareholders United.

“If they do not want to join us, we would ask that they ‘pledge’ their shares to our cause, not in a legal sense, but to agree not to sell their shares to Mr Glazer.”

Ultimately, the key to the furure ownership of the club could lie the Cubic Expression partnership of John Magnier and JP McManus, which owns 29% of MUFC.

“The Cubic stake is crucial in this affair, ” said Mr Towle.

“We have no knowledge of what their intentions are, and clearly (this is) something we will be thinking carefully about over the next couple of days.”