Royle: City claim he's victim of a radio plot by United fans (SFranklin/Allsport)

Maine Road chief operations officer Chris Bird revealed that City have contacted several other radio stations who, like Five Live, hold football phone-ins which they believe have been hijacked in recent weeks by United fans calling for manager Joe Royle to be sacked.

The main target for the succession of complaint calls has been Richard Littlejohn's Saturday evening 606 programme on Five Live.

Members of the public purporting to be City supporters have phoned in, deriding Royle and the club - often using the word 'massive', which relates to the claim that the Maine Road club are too big to be anywhere but the Premiership.

Littlejohn, who took one such call after City's 4-0 defeat by Leeds at the weekend, suggested that an on-air campaign was being mounted.

Bird said: 'We have spoken to Richard and to other people at BBC Radio 5 Live, along with other stations.

'It appears that there is a group of United supporters who are playing tricks. At first the whole thing just seemed mischievous, but the campaign has gone on too long and is too concerted for us to ignore it.

'Richard Littlejohn and his staff have promised to start vetting all the calls his programme gets from so-called City supporters, and other stations have promised to do the same.

'Richard, especially, had begun to work out what was going on. We have told all the other stations to be aware of the problem.'

A Radio 5 Live spokesman said: 'Our highly-trained staff always make sure that calls are fully checked beforehand but sometimes disingenuous callers slip through the net and we will endeavour to avoid similar instances in the future.'

Royle came under fire from supporters at Maine Road last Saturday after his side's latest defeat. A fortnight earlier, when Charlton Athletic beat City 4-1, thousands of fans staged a mass exodus.

City, with striker Paul Dickov facing a six-week injury lay-off, Kevin Horlock out for two months and Mark Kennedy an absentee for another three weeks, face fellow relegation candidates Derby County on Saturday.

But City chairman David Bernstein has intimated that even if City do return to the First Division, Royle will stay.

Bird made it clear that the more the fake fans attempt to create problems for the club and manager, the more the board will stand behind their man.

The campaign is understood to be staged by United supporters seeking revenge following a local newspaper poll conducted in 1995 on Sir Alex Ferguson's future.

It came after United had failed to win a trophy that season and Ferguson had just sold crowd favourites Mark Hughes, Andrei Kanchelskis and Paul Ince.

Fifty-three per cent of voters suggested that Ferguson should be replaced - but it is now understood that almost all of those who voted for him to go were Manchester City supporters.

But Bird insisted: 'This is a far more vindictive, worrying thing. The longer it goes on, the more the likelihood is that real City supporters will be fooled into believing there is substance behind the suggestions that Joe Royle should be forced out.

'What these people don't realise is that as a club, a board and a manager, we have never been closer - and that is the way it will remain.

'As the chairman says, Joe has done a remarkable job here and will be given the time to get things right.

'We appreciate that the real supporters have every right to voice their criticisms and concerns.

'Joe, especially, respects their right to do so because he understands, as a former City player himself, what they have been through over the years.