Shadow home secretary Yvette Cooper has paid tribute to PC Ian Dibell who was shot and killed in Clacton-on-Sea.
Ms Cooper said "I am shocked and appalled by the terrible news from Essex tonight and our thoughts are with the family, friends and colleagues of Pc Ian Dibell.
"We are all reminded that police officers on or off duty put themselves in harm's way to protect the public and they have our greatest admiration for their bravery, for what they do and the risks they take daily to keep us safe.
"It is important to remember that the suspect in this shooting is still at large and police officers are still searching for him.
"We all wish this a speedy and safe resolution tonight."
A major manhunt is underway for the gunman who has been named by senior officers as Peter Reeve.
People living in the Essex street where an off duty policeman was shot dead have been describing what happened. One neighbour, who did not want to be named, said the gunman had crashed a car in an alleyway near a local doctor's surgery.
He said doctors later rushed out to help the men who had been shot.
Another neighbour said: "The first indication I had was what sounded like car doors being slammed.
"I went to look out into the street and there were all these police cars. All I could see were police cars and my friends were then phoning me telling me to stay inside and keep my doors and windows locked."
A major manhunt is now underway for the gunman who has been named by police as Peter Reeve.
Tributes have been paid to the Essex police officer who has been shot and killed in a street at Clacton-on-Sea.
PC Ian Dibell died from shotgun wounds. A second, as yet unnamed, man has been seriously injured.
Paul McKeever, chairman of the Police Federation of England and Wales, paid tribute to Pc Dibell, saying: "This is extremely tragic and devastating news. Police Constable Ian Dibell demonstrated remarkable courage and bravery whilst off-duty and has paid the ultimate price.
Mark Smith, chairman of the Essex Police Federation, added: "This is a terrible tragedy and our thoughts and prayers are with Pc Ian Dibell's family, friends and colleagues at this extremely sad time.
"This appalling incident highlights the dangers that police officers face every day."
A major manhunt is currently underway for the gunman who has been named by police as 64 year old Peter Reeve.
A police officer shot and killed in an Essex seaside town has been named locally as PC Ian Dibell.
Police believe the gunman, who has so far evaded capture, is 64 year old Peter Reeve.
A press conference is due to be held this evening at Essex Police HQ in Chelmsford where more details are expected to emerge.
Essex Police investigating the murder of a policeman who was gunned down in Clacton-on-Sea have issued a photograph of suspected gunman Peter Reeve.
People living in the area are being warned not to approach him.
A major manhunt involving armed officers is now underway in the seaside town.
Police have named a man wanted over the fatal shooting of an Essex police officer.
A major manhunt is underway for 64 year old Peter Reeve following the shooting at Clacton-on-Sea in Essex.
Reports that a man shot and killed at Clacton-on-Sea in Essex was a serving police officer have been confirmed by the chairman of the Police Federation.
Paul McKeever has written on Twitter: "Every police officer in the country is thinking of our colleagues in Essex.
"Our thoughts are with the family and friends of our colleague who has been killed in Essex. It's a very sad day indeed."
As a hunt for the gunman continues Essex Police have refused to confirm the victim's identity or that of a second man seriously injured by shotgun wounds.
As darkness falls on the Essex seaside town of Clacton-on-Sea a major police manhunt has so far failed to track down an armed gunman who has killed one man and seriously injured another.
Unconfirmed reports say the victim was an off duty police officer.
A second man is said by police to be in hospital with serious leg injuries.
Police marksmen armed with assault rifles and handguns and wearing body armour have been searching the area around the quiet residential street where the shootings happened.
Residents living near the scene of a fatal shooting at Clacton-on-Sea in Essex appear to be leaving the area for the night as police continue their hunt for the gunman.
ITV Anglia correspondent Victoria Lampard says a group of about a dozen people, carrying overnight bags, have left the area.
Senior officers had earlier warned people living in the area to stay indoors.
A major manhunt is underway as police search for the gunman who is believed to be armed with a shotgun.
Armed police searching for a gunman who has killed a man in Clacton appear to be widening their search.
ITV Anglia correspondent Victoria Lampard is at the scene of the shooting. She says an "eerie silence" has descended on the area as residents are told by senior officers to stay indoors.
A police helicopter and dog teams have joined the search in the Essex seaside town.
Earlier police activity has failed to locate the gunman who is believed to be armed with a shotgun.