Former England captain Michael Vaughan says he would tell Joe Root to step down if he asked for his advice.
Root, who has been Test captain since 2017, is under pressure with England winless in nine games and having only won one of their past 17.
They have lost their last four series, including a 4-0 Ashes defeat and a 1-0 loss in West Indies, which ended with a 10-wicket defeat on Sunday.
"He's taken it as far as he possibly can," Vaughan told BBC Radio 5 Live.
Vaughan, who has known Root since he played for Sheffield Collegiate growing up, added: "If he rings me in the next week and asks for some advice I'll be dead honest - I'd tell him to step down.
"Will England be any worse off not having him as a captain? I don't think they would, because they are going to get his runs and a senior player.
"They'll get a great role model - I don't think there is a better role model in English cricket."
Root has led England in a record 64 Tests, winning 27 games - more than any other captain - but losing on 26 occasions, which is also more than any other skipper.
His position came under pressure after the Ashes defeat but said he wanted to continue, and he reiterated that on Sunday, saying he is "very passionate about taking the team forward" and he had "the support of the changing room".
England are without a director of cricket and head coach after Ashley Giles and Chris Silverwood left the respective roles following the Ashes, with Sir Andrew Strauss and Paul Collingwood taking up interim roles for the West Indies series.
Both permanent appointments - and a decision about the captaincy - are expected before England's next Test against New Zealand on 2 June.
Vaughan, who captained England 51 times between 2003 and 2008, added: "I wouldn't want the new director of cricket or head coach to sack him - he's deserved the right to go on his own ground.
"During his reign I don't think he has been helped at all. His first Ashes series there was the Ben Stokes incident, then we had the white-ball reset, then he's had Covid and it's been very difficult.
"But, I always think captains should pride themselves on maximising every ounce of potential in the changing room. I just look at the team and ask why did they perform so under their potential? That would be a real concern for me.
"Tactically he has been poor. It has been a common trend under Joe - he hasn't managed to grab a game. If he does carry on he'll really need someone who can drive the tactical side of the game with him."
Former England assistant coach Paul Farbrace told 5 Live that he would decide it was "probably time for a change" if he took up the vacant head coach role.
"He is still England's best player but we've got a stage where we probably need to say 'come on, we need someone'. When he gets home he may think very differently about this," said Farbrace.
However, James Anderson, who is England's all-time leading Test wicket-taker, voiced his support for Root: "If you get the right people in those two jobs above him then he can still do a really good job."
Collingwood, who is interested in the permanent coaching role, also told BBC Sport that Root had been "magnificent" in the West Indies and "shown a real drive and determination to turn things around".
'I don't see a future England captain'
If Root was to stand down, a lack of a ready-made replacement is a concern, with all-rounder Ben Stokes the most experienced having deputised for Root while he was at the birth of his child in July 2020.
However, speaking after the Ashes, Stokes said he had "never really had an ambition to be a captain", leading to suggestions that England may opt for a shorter-term solution like Stuart Broad, who was left out of the West Indies tour.
"I don't see any replacement to Root doing the role long term," said Vaughan.
"Whoever gets it now potentially could just do it for a few months or until the end of the Ashes next year.
"I don't think Broad is the most stupid suggestion - you've got to be sensible about every name at the moment because we don't have massive riches.
"It is the first time in my lifetime where we've not had a future England captain playing and that is a real concern."
Farbrace, now director of cricket at Warwickshire, said Stokes was the "obvious option" and Broad, who captained England in Twenty20 cricket from 2011 to 2014, was a "good option".
"We may have to go short term and someone like Broad may be a good option for 12 months to get England winning again," said Farbrace.
"What we can't have is picking a player just to be a captain - we can't go back to those bad old days. It has to be someone that is worth their place and someone who is going to consistently play in the next 12 months, that is why Stokes and Broad are the only two options."
However, West Indies all-rounder Carlos Brathwaite does not think that England should add to Stokes' workload - with the 30-year-old a key component of the side in all three formats.
"I don't think Ben Stokes can do it long term because of the amount of energy that he puts into the game," Brathwaite told BBC Radio 5 Live.
"He is a leader and there are certain players like Stokes and Jonny Bairstow who don't need the title of captain to be a leader or help drive the culture."
Vote: Who should captain England in first New Zealand Test?
After the Ashes series we asked you who you wanted to be England captain on this tour of West Indies. The vote saw 58% keeping faith with Root.
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