Roy Keane believes Alex Ferguson is still trying to exert "control and power" at Manchester United despite retiring as manager in the summer.

The Republic of Ireland assistant manager, Ferguson's midfield driving force at United between 1993 and 2005 says his former club manager has a "massive ego", rating his former Nottingham Forest boss Brian Clough as the best manager he had worked with.

United have endured a difficult start to life under Ferguson's successor David Moyes, having lost three Premier League games at Old Trafford already this season to sit ninth in the table.

Keane said of Ferguson, now a director at United: “Everything is about control and power. He’s still striving for it now even though he’s not manager. There’s massive ego involved in that.”

Keane, who left United in 2005 after a fall-out with Ferguson, was speaking in an ITV4 documentary called 'Keane and Vieira: The Best of Enemies' which airs on Tuesday night concerning his rivalry with former Arsenal captain Patrick Vieira.

He said that his relationship with the former United boss is now “non existent”.

The Irishman even took issue with Ferguson praising him in his autobiography for “covering every blade of grass” in the 1999 Champions League semi-final second leg against Juventus.

Keane added: “Stuff like that almost insults me. I get offended when people give quotes like that about me. It’s like praising the postman for delivering letters.”

Keane admitted he had cried in his car when his United career came to an abrupt end over a candid interview he gave to the club’s in-house television station criticising his team-mates.

He said: “Of course I was upset: I did shed a few tears in my car for about two minutes. But I also told myself I had to get on with my life.

"I walked out with nothing, I had no club lined up and I was injured. I told David Gill I had been injured playing for Man United. I could have played for Manchester United easily for another couple of years."

Keane laughed off the furore surrounding the infamous MUTV interview and said he felt the row between Ferguson and then club director John Magnier over the stud rights to racehorse Rock of Gibraltar had to have had a "negative effect" on the club.

Keane said: “I managed the dressing room: that was my job. If people didn’t think (the Rock of Gibraltar row) had a negative effect on the club then they are in cuckoo land.”

Keane said Ferguson’s strongest trait was his “ruthlessness”, while labelling “loyalty” his biggest weakness.

And now Ferguson has retired, Keane revealed he and his son have season tickets at Old Trafford.

Keane revealed he twice agreed contracts with top European clubs to quit Manchester United, only to change his mind at the last minute.

Twice Keane revealed he nearly left Old Trafford, agreeing contract terms with Bayern Munich and Juventus, but in both instances he changed his mind.

But the former Republic of Ireland midfielder admitted “fear” held him back.

He said: “I wouldn’t say I had regrets about not going abroad but I think it would have been a nice experience to play for a different team.

“When my contract ran down on a couple of occasions I spoke to a couple of clubs, Bayern Munich, Juventus. And yeah I was very tempted I have to say, but there was a bit of fear.

“Contracts were agreed but I just never felt strong in wanting to go for it because I was very happy at United.”

Keane rated quitting Ireland’s pre-World Cup training camp in 2002 as among his biggest regrets in football.

Confirming his broken relationship with Ireland manager Mick McCarthy was at the centre of that 2002 walkout, Keane said his international career remains wrapped up in “frustration”.

Keane said: “It would have been nice to have played. A lot of people were disappointed, particularly my family.

“Mick did say to me that if you don’t respect me how can you play for me? And what I should have said was I wasn’t playing for him I was playing for my country, but by then it had gone.

“I just felt we needed to change our attitudes a little bit. That we at least prepare as well as the Germans and the Brazilians.

“Why not prepare as well as them?

“People always think I was looking for perfection: what I was looking for was progress.”