Rishi Sunak has insisted he will introduce a security law in the wake of the Manchester Arena bombing after criticism over delays.
The PM said new legislation, dubbed Martyn's Law in memory of one of the victims Martyn Hett, will ensure stronger protections against terrorism in public places.
Mr Hett, 29, was one of 22 people killed during the attack at the end of an Ariana Grande concert on May 22 2017.
The new rules, which Mr Hett's mother Figen Murray has long campaigned for, will cover all of the United Kingdom and require venues and local authorities to have preventative action plans against terror attacks, the Government said.
Mr Sunak said he is committed to working with Mrs Murray to improve security measures at public venues, with the Government planning to publish draft legislation in early spring.
Senior police officers last month wrote to the Prime Minister to raise concerns about the government’s failure to deliver on its promise to introduce a law to improve security at public venues. The letter, also signed by relatives of terrorism victims, said the delay was "dangerous".
Martyn's Law will follow a tiered model linked to the size of the expected audience.
A standard tier will apply to locations with a maximum capacity of more than 100 people. Venues will need to undertake low-cost effective measures such as training, information sharing, and completion of a preparedness plan.
An enhanced tier will focus on high-capacity locations. Those that can hold 800 or more will be required to undertake an additional risk assessment that will inform the development and implementation of a thorough security plan.
The Government will also establish an inspection and enforcement regime, issuing sanctions for breaches, and will provide statutory guidance and bespoke support.
Speaking days after her son would have celebrated his 35th birthday, Mrs Murray said: "The Government taking this seriously and promising to act is the best birthday present I could have asked for on Martyn's birthday.
"While nothing can bring Martyn back, this news means that others like him will be better protected.
"Common-sense security in public venues - big or small - could mean fewer suffer what myself and the families of Manchester have had to endure.
"Now we need urgent action to get this into place. I hope that this law will now be introduced in the current session of Parliament so we can get this done as soon as possible."
Praising Mrs Murray's campaign, Mr Sunak said: "The way the city of Manchester came together as a community in the wake of the cowardly Manchester Arena attack, and the amazing work of campaigners like Figen Murray who have dedicated their lives to making us safer and promoting kindness and tolerance, is an inspiration to us all.
"I am committed to working with Figen to improve security measures at public venues and spaces and to delivering this vital legislation to honour Martyn's memory and all of those affected by terrorism."
Home Secretary Suella Braverman thanked Mrs Murray and her campaign for their "tireless efforts".
"Protecting the public from danger is a key responsibility of any government. The terrorist threat we face is diverse and continually evolving, which is why this legislation is so important.
"I would like to thank Figen Murray and the Martyn's Law campaign for their support in the development of this vital reform.
"Their tireless efforts have helped inform our approach and the heart-breaking stories from survivors and their families are a constant reminder as to why we must deliver on this commitment to work together to improve public security."