Cristiano Ronaldo must "stand up now and speak" and not wait to lift the lid on his situation at Manchester United, says Gary Neville.

The Red Devils' failure to secure a Champions League berth last season led to reports Ronaldo told the club he wanted to leave just under a year after returning to Old Trafford from Juventus.

A shambolic start to life under Erik ten Hag, which saw an opening home defeat to Brighton and Hove Albion followed by a 4-0 drubbing at Brentford, has only exacerbated the situation.

However, despite being linked with a host of Europe's biggest clubs it appears there are a lack of viable options for Ronaldo with Chelsea and Bayern Munich said to have rejected the chance to sign him, while a potential switch to Atletico Madrid would be wildly unpopular with the club's fanbase due to his status as a Real Madrid legend.

It was even suggested after the humiliating loss to the Bees that United were considering terminating the Portugal great's contract if his attitude does not improve.

Ronaldo teased offering his side of the story in the coming weeks by writing on Instagram: "They know the truth when [sic] interview in a few weeks. Media only speaks lies. I have a notebook and in the last few months of the 100 news that made only five [accurate] hits, imagine how things are."

Ronaldo's former team-mate Neville has urged the 37-year-old not to wait to speak out, with the club in "crisis".

"Why does the greatest player of all time (in my opinion) have to wait two weeks to tell Manchester United fans the truth?" Neville wrote on Twitter.

"Stand up now and speak. The club is in crisis and it needs leaders to lead. He's the only one who can grab this situation by the scruff of the neck!"

Earlier this week, Neville also expressed his fear letting Ronaldo go could see United slump to a bottom-half finish in the Premier League this season if they do not sign reinforcements.

"As I sit here today now, and I think there’s a massive decision to make on Cristiano Ronaldo, I think they’re damned if they do and damned if they don’t,” Neville said on Sky Sports' Monday Night Football.

"Before these two results, I said the best thing to do is facilitate a move for Cristiano and for the club, because he's obviously not happy and the club are not happy with him.

"The problem is now that if they lose him then there's nothing left in terms of goal scoring.

"I genuinely think that if they don't bring players in, in these next couple of weeks, or if they bring poor players in, and he leaves, I genuinely think they could finish in the bottom half of the table. I think it's a bottom half of the table team.

"That's a massive statement and could look stupid at the end of the season.

"They're absolutely demoralised and shot to pieces, I think it's really bad in there. Ten Hag in pre-season had got them to a really confident level, but basically they've gone back to default and the old things have come back."

United host fierce rivals Liverpool on Monday as they aim to quickly inject life into their season.