The Manchester City goalkeeper was dropped for almost two months earlier this season, after a high-profile blunder at Chelsea in October cost Manuel Pellegrini's men a share of the spoils at Stamford Bridge.
Hart's form has been consistent since he regained his first-team place towards the end of December, but Shilton believes the 26-year-old now has little room for error ahead of this summer's showpiece in Brazil.
"I didn’t think that having a bad spell like he did was a good thing, because I don’t think you should have a bad spell as a goalkeeper," he told FourFourTwo. "You have a game to forget sometimes, but as a top keeper you’ve got to be back on song and make sure you don’t have a bad spell to get dropped.
"I think the way Joe came through so quickly from Shrewsbury was quite outstanding really. He quickly developed into a goalkeeper everybody was saying was one of the world's best, and that's a lot of pressure.
"Maybe he took his food off the pedal, or he just hit a brick wall or something like that. Maybe the rest actually did do him good, because since then he's looked a lot sharper than he was.
"Either way, Joe’s obviously got the situation now where any mistake is going to be costly. He knows that, so he’s got to keep being consistent and not make mistakes. The other keepers really haven’t had a chance to prove themselves at international level, although they’re doing OK at club level. We’ve got a good crop of keepers with a bit to prove."
England play their final friendly before Roy Hodgson names his provisional squad for the World Cup against Denmark at Wembley on Wednesday night.
Hart is currently the Three Lions' most experienced goalkeeper at international level, with 38 caps separating him from Ben Foster (6), John Ruddy (1) and Fraser Forster (1). Shilton, however, believes there is no cause for concern for Hodgson and his lack of options - so long as Hart continues his steady run.
"I’d probably be less worried now Joe seems to have got back into the first team," said the former Leicester City man. "He’s our first choice and most experienced keeper, although Roy Hodgson hasn’t really got anybody else.
"I think Ben Foster has got good technique and is a very good goalkeeper, but he hasn’t played a lot at international level. Fraser Forster has a lot of potential, but I don’t think it’s helping him playing at Celtic. He should be playing in the Premier League where people can get a better idea of what he's made of."
With 125 appearances, Peter Shilton is England’s most capped football player. Celebrating the launch of the Wasgij Original 21 Football Fever jigsaw puzzle, Jumbo Games is running a promotion offering the chance to watch England take on Uruguay alongside the legendary goalkeeper on June 19, 2014.
