Emergency response crews attend the scene after one of the five acid attacks that took place in London on Thursday - REUTERS

Ministers are coming under pressure to tighten the laws on the sale and possession of acid and other corrosive substances amid growing fears they have become the “weapon of choice” of teenagers.

Calls for changes to the law followed a spate of five acid attacks in the space of a little over an hour that left one victim with “life-changing” injuries.

Another victim told how he felt his “face was burning”. Two boys, aged 15 and 16, were arrested on Friday in connection with the attacks on moped riders on Thursday night.

Scotland Yard figures show the number of attacks using corrosive substances rose to 458, more than double the figure in 2014.

The Home Office said on Friday evening it was urgently working on an action plan to curb the use of acid, including restricting its sale to under-18s.

Campaigners told The Telegraph that crime gangs were switching to acid and ammonia because laws had been tightened on possession of knives.

Sulphuric acid at 91 per cent strength can be bought cheaply over the counter in shops and DIY stores as a drain unblocker. There is no age restriction for those buying it. Ammonia is similarly available.

Chart: Acid attacks across the UK

Jaf Shah, of Acid Survivors Trust International, said: “Concentrated acid is clearly becoming the weapon of choice for gangland kids.

“For the perpetrators, using acid is a ‘safer’ crime to commit because you are not going to be charged if you are caught in possession of it. It is very cheap and kids of any age can make a cash payment and cannot be traced.

“The Government needs to urgently introduce measures to make concentrated acid and ammonia available only for over-18s and with a credit card.”

Map: East London moped acid attacks

Dr Simon Harding, a criminologist at Middlesex University and an expert on gangs, said gang members were aware that “the charges are more serious if you are caught with a knife and the tariff for prison sentences are much higher”.

Stephen Timms, a former Labour minister, called for tougher sentences, a new offence of carrying concentrated acid to be introduced and the licensing of its purchase.

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Mr Timms, who will lead a debate in the Commons on Monday on the issue, said: “Carrying acid should in itself be an offence. Carrying a knife wouldn’t have been an offence some years ago. I think there’s been a pretty effective change – the same change should be made for acid.”

Mr Timms said that the law could be changed so as not to punish those buying the substances for legitimate use, such as drain cleaner, in the same way that people are not automatically criminalised for buying kitchen knives.

Cressida Dick, the Metropolitan Police Commissioner, disclosed that the Home Office is working with her force to look at changes in the law.

She told LBC radio that the attacks on Thursday night were “completely barbaric” and added: “We are concerned because the numbers appear to be going up.

“We will arrest people, we will enforce the law as we can, and we are working very closely with the Home Office to try to see if there are any changes in the law required.”

A Home Office spokesman declined to say what changes were being made. “We are working on it,” they said.

Under sentencing laws introduced in 2015, repeat offenders caught in possession of knives are automatically sentenced to a minimum six months in jail. No such powers exist for possession of acid.

The growing demands for action will be reinforced by a moving testimony from Katie Piper, a television presenter who survived an acid attack and remains disfigured almost a decade on.

Ms Piper, writing in an open letter in the medical journal Scars, Burns & Healing, said victims face a “life sentence”. She also called for tougher sentencing to act as a deterrent.

Theresa May’s spokesman said the Prime Minister regarded the attacks as “horrific” but insisted there was already an offence of “carrying acid or a corrosive substance with intent to cause harm”.

Night of horror as acid attackers strike at will

The delivery rider on his moped was stopped at traffic lights on his way home. Suddenly he felt a liquid – he thought at first it was water – trickling down his face. Then followed a terrible stinging sensation.

Jabed Hussain, a father of one, was the first victim in a spate of five acid attacks committed over 72 minutes.

As the horror unfolded, Mr Hussain, a rider for the online delivery firm UberEATS, could count himself one of the luckier ones. His helmet, he is convinced, saved him from suffering devastating injury.

An unknown victim is treated with water by police

On Friday night, two children, aged 15 and 16, remained in custody on suspicion of carrying out the terrifying attacks across fashionable East London. Experts fear acid and ammonia have become the latest weapons of choice among street gangs. One report suggested that many delivery riders, fearful of coming under acid attack, are now refusing to work after dark. Another victim worked for Deliveroo.

The fourth victim in Thursday night’s spree – all were riding mopeds – suffered “life-changing” injuries. The extent of the injuries suffered by the others is unclear.

“I was lucky because I was wearing a helmet which is totally burnt, as was the hoodie,” said Mr Hussain, 32, recounting his ordeal. “They pulled up on my left hand side on a motorbike; then suddenly I felt something wet on my face. I thought it was water. My face was burning. I was screaming for help and as the liquid on my face was drying, it was getting more and more burnt.

Victims | 'The aftermath is a life sentence'

“I had never felt anything like it before. It was like fire on my face, extreme fire. I think most of the acid, at least half, hit my helmet and trickled down, but some of it came through to my visor, on to my face and reached my lip.”

A bystander raced into a nearby Co-Op – police timed the attack at 10.25pm – and poured water on his face. Police and ambulance crews arriving on Hackney Road then poured litre upon litre of water over him, having first pulled off his T-shirt and removed his helmet.

“I’m the lucky one,” said Mr Hussain, “Other people who were injured, their faces were totally burned. One man I walked past at the Royal London Hospital had the left hand side of his face all burned.”

Eyewitnesses heard Mr Hussain’s “piercing screams” as he fought the pain. The attackers stole his moped before speeding off on their motorbikes.

The next incident took place less than 25 minutes later in Islington, over the border from Hackney, where the other attacks occurred. A 44-year-old moped rider was ambushed at St Paul’s Road and Highbury Corner, Islington; the men fleeing empty-handed. Police said yesterday they were still waiting to discover the extent of the victim’s injuries.

Fifteen minutes later, the pair struck again, this time in Shoreditch High Street, a popular night time hangout. Staff in the Drunken Monkey pub were looking out the window when they saw a moped pull up about a yard ahead of a delivery rider. The pillion passenger turned and sprayed what was described as “ammonia-like” liquid in his face. Their 52-year-old victim suffered burns to his face.

A witness, who asked not to be named, said: “The passenger just turned around and sprayed liquid at him. He had his visor down, which helped him. The guy on the moped sat there in shock and then a kid pushed him off and tried to nick his bike.” But the victim fought back and the acid assailants raced off, again empty-handed. Staff ran out of the pub and dragged the victim inside. They smelled ammonia and, thinking quickly, poured vinegar on his face to neutralise the corrosive liquid.

Thirteen minutes later in Cazenove Road at the junction with Upper Clapton Road, a 24-year-old moped rider had a corrosive substance sprayed in his face. His injuries, according to police, are “life-changing”.

A woman, who lives in flats off Upper Clapton Road, who did not want to be named, raced to her window after hearing screams. She heard someone shout: ‘Oi, what do you think you’re doing?’ ”

An unknown victim is treated with water by police at the scene

Again the gang was thwarted in the plan to steal the moped. Twenty minutes later, they struck again and for the final time. On this occasion it was in nearby Chatsworth Road, home to bijou shops and restaurants. A 33-year-old man was robbed of his moped. He went home before calling police and taking himself off to hospital.

A 16-year-old was arrested in Islington in the early hours yesterday after being tracked by CCTV; a 15-year-old was detained in Stoke Newington in Hackney later in the day.

Chief Inspector Ben Clark, from Hackney Borough, said: “These are hideous offences and must have been very frightening for all of the victims.

“Of late we have seen more attacks using corrosive substances in London.

“I would urge businesses and parents to challenge those who they think may be trying to obtain or carry these substances as this could help prevent serious offences and life changing injuries being caused.”