Stormzy has said Britain is “definitely, 100%” racist and that this has worsened under Boris Johnson because his comments have emboldened people with racist views.

The grime artist, who has just released his second album, Heavy is the Head, made the comments in an interview with the Italian newspaper La Repubblica. When asked if Britain was still racist, the musician said “definitely, 100%” even if it was “hidden”.

“It’s like: ‘Oh no, we’re not racist’. But there’s a lot of racism in the country,” he said. “The difficult thing with the UK is, as you said, in Italy it’s a clear problem, whereas trying to explain that Britain is a racist country [to a British person] is the most difficult thing ever. They think: ‘No, it’s not. Stormzy you’re successful. Look at London, there’s loads of black people …’ It’s a more difficult case to fight.”

Stormzy said the prime minister was a “figurehead” whose actions had made it more acceptable to say racist things in British society. “If the top person can openly say this racist thing – the ‘piccaninnies’ remarks, ‘watermelon smiles’, comparing Muslim women to a letter box – if that is our figurehead, the top man, the leader we have to follow, and he openly says these things, he encourages hate among others.”

He said since Johnson had been in office the situation had deteriorated, with people who hold racist views feeling emboldened to express them in public.

“Before, people had to hide their racism. If you felt something bad about about black people, about Muslims, you had to shut up. Now these people have the confidence to come out in public to say everything. This is scary to me, that scares the shit out of me.”

Stormzy, whose real name is Michael Ebenazer Kwadjo Omari Owuo, said he would have to carefully consider whether or not he would accept an honour such as an MBE or OBE if offered one. He said it would be difficult to accept an honour “because of the British empire”, but that his mother would be proud if he was offered one.

“It’s got a very dark history. You know, Britain colonised everywhere. It’s something I’d look into and decide in case of.”

Stormzy has been a vocal critic of the Conservative government, and Johnson in particular. His single Vossi Bop contained the line “Fuck the government, and fuck Boris”, which became the slogan of a campaign aimed at unseating him at the recent general election.

This week he was criticised by the TV presenter Piers Morgan for telling a group of children at his old primary school in Thornton Heath, south London, that Johnson was a “bad man”.

Morgan tweeted: “He shouldn’t have done this, and shouldn’t have been allowed to do this.” Stormzy responded: “The kid asked me a question and I replied truthfully, nothing wrong with that Piers lol.”

In the buildup to the general election, Stormzy gave his support to Labour, signing an open letter to the Guardian along with several other cultural figures that backed the party’s pledge to end austerity. In later tweets he described the Labour leader, Jeremy Corbyn, as being the first man in a position of power who is “committed to giving power back to the people and helping those who need a helping hand from the government the most”.

He was also involved in a Twitter dispute with the Conservative MP Michael Gove who quoted his lyrics and criticised his decision to back Labour. Observers said a white, middle-class politician imitating a young black grime MC on social media was the equivalent of “Twitter blackface”.

During his headline Glastonbury set in June, Stormzy wore a stab vest with a union flag on it, designed by Banksy. As he performed the words “knife crime” appeared lit up behind him, and there was an excerpt from a speech by the Labour MP David Lammy on the issue. Lammy tweeted that Stormzy had used the performance to “speak out about the injustice of young black kids being criminalised”.

In the Repubblica interview, Stormzy explained how his style and approach to music had changed. “Now I am rich, I no longer live in the dark streets of Croydon, I am no longer as angry as before,” he said. “Everything changes and so you look for a new voice. But the important thing is always to be honest with yourself.”

Stormzy is the latest high-profile black British cultural figure to say they would consider turning down an OBE or MBE. The spoken-word artist and podcaster George the Poet said he rejected an honour earlier this year because of the “pure evil” perpetrated by the British empire. The poet, whose real name is George Mpanga, told the Guardian the honours system needed a dramatic overhaul.

“If you can get me – a child of Africa, whose grandfather died in exile as a result of British meddling in Uganda, whose great-great-grandfather resisted the British invasion of his country – to accept an MBE, what would my descendants make of that? What would my ancestors make of that?” he asked. “It’s not fair that in order to accept this accolade, in order to accept this recognition, I have to submit to that interpretation of empire.”

Stormzy’s new album went to the top of the streaming charts when it was released on 13 December, with several songs appearing in the top 40 singles charts.