The head of “Britain’s FBI” has warned the Mr Bigs of the underworld there will be “no one beyond the reach” of the new crime-fighting agency on the day it goes live.

With a budget of nearly half-a-billion pounds a year, the National Crime Agency (NCA) will lead the fight against the estimated 37,000 criminals involved in serious and organised crime that hits the UK.

More than 4,000 NCA officers will tackle crime under four commands, organised crime, economic crime, border policing and child exploitation and online protection, alongside a National Cyber Crime Unit.

Asked if the new law-enforcement arm would be able to bring the fight to the “higher echelons” of organised crime, NCA director general Keith Bristow said: “To be clear, there will be no one beyond the reach of law enforcement or beyond the reach of the NCA.

“Those people involved in the most horrible activities can expect the most comprehensive and robust response.”

The launch of the NCA spells the end of the Serious Organised Crime Agency (Soca), which is to be absorbed into the new organisation.

Proposals for the new agency were first unveiled by Home Secretary Theresa May in July 2010 as part of a broader shake-up of the policing landscape.

Announcing the new US-style agency, Mrs May said it would have a sweeping new power to step in to directly task and co-ordinate police forces in a bid to tackle organised crime and secure the UK’s borders.

Too many of the near-6,000 organised crime gangs in the UK were escaping justice and a tough new approach was needed, she said.

The NCA has an annual budget of £463 million for resources and £31 million for capital, Mr Bristow confirmed.

The NCA will run the country’s first national intelligence hub, place investigators at UK ports to tackle border crime such as human trafficking and will track down child-sex abusers online.

It will also place around 120 officers overseas in 40 different countries.

Mr Bristow, a former chief constable of Warwickshire Police, said unlike Soca, the NCA would not operate as a covert organisation and wants to be recognised by the public.

Video Loading

Some of its officers will wear jackets and caps emblazoned with NCA when on operations.

“We’re going to be visible,” he said. “We want the public to know who we are, what we do, what we’re delivering, to understand the serious and organised crime threat that effects every neighbourhood and every citizen throughout the UK.”

He added: “Frankly, we want the criminals to know who we are, because we want them to fear our attention.”

The NCA will also be recruiting “special” officers - volunteers like special constables in police forces.

NCA specials with expert backgrounds such as in cyber or the financial sector are set to join the agency.

Home Secretary Theresa May said: “I want to make Britain a hostile environment for serious and organised criminals, with the new National Crime Agency leading that fight.”

Shadow policing minister David Hanson said: “The National Crime Agency doesn’t match the Government’s hype.

“It is welcome that the NCA has finally arrived after three years of delay and we support strengthening work on organised crime and the hard work of Keith Bristow and his team.

“But most of the NCA is just the rebranding of existing organisations such as the Serious Organised Crime Agency, but with a substantial 20% cut imposed by the Home Office in their overall budget.

“The new organisation is not strong enough to deal with the exponential growth of economic and online crime. It will simply absorb the existing National Cyber Crime but with fewer resources.

“And due to Government mishandling it won’t be able to operate in Northern Ireland leaving a serious operational gap compared to the Serious Organised Crime Agency that it replaced.

“It is extremely worrying that organised crime which crosses between Northern Ireland and the rest of the UK will not be properly dealt with because the Home Secretary mishandled the legislation with the relevant parties in Northern Ireland.

“It is right to have stronger national action on organised crime with the NCA, on child exploitation and on intelligence but the Government has to support this effort and not simply use this as a rebranding exercise to hide substantial policing cuts.”