London police have warned residents to prepare for acid attacks and an inflow of opportunist thugs using the Grenfell fire tragedy as a pretext for trouble at this year’s Notting Hill Carnival.

Performers at Europe’s largest street festival have been urged to carry modified water bottles to treat acid attacks, after a massive surge in gang-related attacks using the corrosive liquid in recent months.

Officers have also spoken to business owners about potential troublemakers at the event, and one told The Times he expects “left wing” activists to cause disruption.

On Tuesday, the Metropolitan force said in a statement they had made more than 290 arrests and recovered 190 knives and 18 firearms in operations “aimed at ensuring that those who intend to cause trouble at Carnival are prohibited from doing so”.

Prior to #NottingHillCarnival, we're disrupting gang crime, drug supply, knife crime & offences that could impact the safety of the weekend — Metropolitan Police (@metpoliceuk) August 22, 2017

In June, figures revealed crime in England and Wales had seen its largest annual rise in a decade, with violent crime shooting up by 18 per cent.

“I’ve been told by the police there probably will be trouble, relevant to Grenfell,” an unnamed businessman told The Times. “They reckon it will be external. Not from the people living here… I imagine it will be left-wing protesters. They also think gangs and things will be more emphasised.”

He also revealed he had cancelled a planned charity event because of disclosures by police and the threat of disturbances.

Sources at Scotland Yard told the paper about 9,000 officers would be deployed on each day, compared with 6,000 on the Sunday last year and nearly 7,000 on the Monday.

Ansel Wong, the artistic director of Elimu Mas Academy, which works with the carnival bands, said: “There is an issue of acid attacks as well. We as a performing group have to take steps to protect and comply with the Met.

“A simple provision is specially adapted bottles of water. Advice following an acid attack is that you need to sprinkle water on the skin. The cup has to be drilled with water to get a shower-like effect.”

Chief Superintendent Robyn Williams, the Met’s spokeswoman for Notting Hill Carnival, said: “We are committed to ensuring that carnival remains a safe, vibrant and enjoyable event. Troublemakers are not welcome.”

In June, hundreds of open borders and Communist activists hijacked a Grenfell protest outside Parliament, demanding the Tory government was “brought down” and Labour leader Jeremy Corbyn installed in power.

The march came days after the leadership of the Labour Party said they needed “every union mobilised” and for a million people to “get out on the streets” to overthrow the government after the fire.