Sir Alex Ferguson has admitted his biggest regret about Cristiano Ronaldo was that Manchester United only got £80m for him when he joined Real Madrid, and again backed David Moyes.

It was a world record fee at the time, but it has been broken by the transfer of Gareth Bale to the Los Blancos in the summer.

Ronaldo has scored an incredible 238 goals in 233 appearances since moving to Bernabeu in 2009, and Sir Alex Ferguson has now revealed he wanted to ask for £150m for the FIFA Ballon d'Or winner.

“I told David Gill to ask for £150m. Perez would have paid,” Ferguson told Spanish newspaper AS.

“The only thing that hurt me, and I said this repeatedly to David Gill, was that we didn’t demand enough.

“I told David, ‘Ask for £150m’.

“He said, ‘Don’t be silly. They’ll never pay £150m’.

“I said, ‘Ask for it because he’s worth it’.

“We signed the deal. I think it cost £80m or so but I’ll always wonder what Mr Perez would have said if we’d asked for £150m.”

The former Manchester United boss says he is certain that Real Madrid would have paid up to £150m for the Portuguese, which Ferguson believes was the true value for the 23-year-old by the time.

“Considering the fact that they signed Gareth Bale for £85m, I think he would have agreed to pay between £80m and £150m,” Ferguson continued.

“I’m sure he would have because Perez knew perfectly the quality of player he was receiving, as shown by his time at United.

“Furthermore he was only 23. That is the only disappointing aspect.”

Ferguson also commented on the struggles of his successor, David Moyes, and pleaded for everyone to give his countryman more time.

"They (United) will be all right," he added.

"It's early days and there have been a lot of changes. He (Moyes) needs time.

“I was there for 27 years, so with a new manager, it takes time. But they'll be okay."

Do you agree with Ferguson that Ronaldo could be seen as bargain of the century? Have your say in the comment section below.