He said drug testing at festivals has been happening since 2014 with the agreement of local councils and police, but the Home Office decided to enforce the requirement for a Controlled Drug Licence just hours before Parklife, an annual two day festival in Manchester, was set to begin this June.
The Home Office said there has been no change in its policy for the past 50 years.
Mr Lord, who is also the Night Time Economy Adviser to Greater Manchester, on Wednesday called on the Home Office to grant a group authority licence to major drug testing providers such as The Loop so they can test drugs on-site at festivals.
Currently a Home Office licence can be issued for drug testing only if providers have a specific, named, permanent premises, Mr Lord wrote in the letter.
He wrote: “Clearly this is problematic for music festivals as they are often held in remote areas and do not have permanent structures on site, instead portacabins are ordinarily used to conduct this on-site drug testing in the presence of police.
“We should be grateful for the Home Office’s view as to whether it would be prepared to grant a group authority licence to the relevant testing providers, for example The Loop, which would as we understand it allow people to supply and possess drugs in accordance with the group authority that does not require a permanent structure.”
The letter comes a month after Mr Lord threatened legal action against the Government over its ban on drug checking at festivals without a Controlled Drugs Licence.
He claimed the Home Office sent an email to The Loop on June 8 stating that any organisation conducting drug testing would require a licence.
This was 48 hours before Parklife festival was to start on June 10, giving organisers no time to apply for a licence, Mr Lord claimed.
The warning was a shock because music festivals in the UK have provided on-site drug testing with the agreement of police and local councils through various organisations and charities since around 2014, he said.
Mr Lord told the Standard on Wednesday: "The Home Office has left me with no option but to step up my threat of legal action in this matter.
"Despite repeatedly voicing my concerns, and those of the festival and night time industries, the Government has chosen to proceed with a dangerous and reckless change in policy which could put lives at risk.
"This policy was working perfectly well, and I have no doubt it saved countless lives in the past, when festivals like my own, the police and specialist drug testing agencies worked seamlessly together to keep people safe.
"I am therefore respectfully asking the Government to do the right thing on behalf of parents, artists and festival-goers and rethink their decision."
Night Time Industries Association CEO Michael Kill said: “People across our industry are increasingly concerned about the actions of the Home Office and their potential effects on the wellbeing of customers.
“We need solutions, not denials, and that is why we’re stepping up our legal action against the government.”
A Home Office spokesperson said: “There has been no change in our position. For the past 50 years, drug checking providers must have a licence to test controlled drugs, including at festivals, which they can apply to the Home Office for.
“We continue to keep an open dialogue with any potential applicants who wish to apply for a licence.”
Festivals aiming to test drugs off their site this summer have to work with the police and a Home Office licenced drug testing provider.
In a letter to Mr Lord dated July 14, responding to his pre-action letter, the Home Office said it did not accept that it had “changed policy” but has consistently held the requirement for a Controlled Drugs Licence.
The Home Office said production, supply and possession of controlled drugs is “generally unlawful save when carried on by certain designated persons carrying out specific functions, or under a Controlled Drugs Licence”.
“This has been the law for many years,” the Home Office said. “It is not understood that this view of the law is controversial.”
Mr Lord said that an application for the Controlled Drugs Licence costs thousands of pounds and takes three months.
He said the letter informing The Loop of the licence requirement was “procedurally unfair”, “irrational” and left festival goers at risk of death.
Under the Home Office requirements set out to The Loop in June, the letter said that “substances would have to be transported away from the festival to the premises identified in the licence in order to be tested”.
“This requirement would render the testing, for all but the largest of festivals, prohibitively expensive and, even for the largest of festivals, so time consuming as to nullify its effect.”