Boris Johnson has insisted the wheels are “staying very firmly on the bus” as his election campaign arrived in the South West – with rival activists demanding “Boris out”.

The Prime Minister sang songs, held Rosie the rabbit, failed in a Where’s Wally? search and corrected a pupil who shouted “boobies” when looking at a picture of the Incredible Hulk during a school visit.

Labour, Liberal Democrat and climate change campaigners gathered outside the school near Taunton – some shouting for him to leave his post and others protesting against austerity and the Government’s approach to the environment.

The PM visited West Monkton Primary School for his first stop in the South West.

He wished happy birthday to a staff member before heading to see the Little Herons Nursery at the school where Rosie the rabbit lives.

Mr Johnson joined in with the Little Peter Rabbit song but did not join pupils in doing the bunny ears action with his hands.

The PM then suggested singing The Wheels On The Bus, remarking: “The wheels are staying very firmly on the bus.”

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Boris Johnson during a visit to West Monkton Primary School (Stefan Rousseau/PA)

Rebecca Pow, the Tory candidate seeking re-election in Taunton Deane, joked: “I think the kids are better at singing than the Prime Minister.”

Before leaving the room, Mr Johnson noted: “Rosie was very well behaved.”

He then watched a pupil solve a Rubik’s Cube in around two minutes.

The PM said: “That’s fantastic. Is that the main subject on the curriculum? I cannot do it for toffee.”

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The PM watches a pupil complete a Rubik’s Cube (Stefan Rousseau/PA)

He also drew a fish to highlight the risks of plastic in the oceans, although he said his creation looked like a frog before morphing into a “sharky-type fish”.

Mr Johnson asked a separate group of pupils about their favourite book before saying: “Have you got the Incredible Hulk? That’s the one I like.”

While looking at a book featuring the Hulk, one pupil shouted “he’s got boobies”, to which the PM replied: “Those aren’t boobies, they are muscles.”

Mr Johnson read an extract from the book before asking the children if they were stronger than the Hulk, to which several replied yes.

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Mr Johnson struggles to find Wally (Stefan Rousseau/PA)

He then asked the children to help him with Where’s Wally? – a nod to the book he was holding rather than anything else.

“I cannot find Wally, I give up,” Mr Johnson concluded.

Ahead of the PM’s departure, chants of “Boris Out” could be heard outside the school from some of the activists.

Another shout included “Keep the oil in the soil”, while criticism of austerity policies could also be heard.