The Hampshire father of a man ''needlessly'' killed in a plane crash with eight others in New Zealand has called on the country's prime minister to review aviation safety.

Chris Coker, whose son Bradley died in 2010 while trying skydiving, said that adventure tourists to New Zealand will not be safe until better regulation is enforced and that young people should ''think twice'' before pursuing any adventure activities in the country.

His call comes after an air accident investigation report found that at least two of the tandem-master crew who would accompany the skydivers in the aircraft had taken controlled drugs and one had taken cannabis during that day's operations.

The report was critical of the Civil Aviation Authority in New Zealand which it said did not do enough to monitor the safe operation of the company and called on the New Zealand government to introduce testing for drugs and alcohol.

Web designer Mr Coker, 24, from Farnborough, Hampshire, boarded the Walter Fletcher FU24 light aircraft operated by Skydive NZ at Fox Glacier, South Westland, on September 4 2010.

The aircraft was a 30-year-old badly converted crop sprayer with a new engine but it was overloaded and none of the passengers were wearing a seat belt, which is allowed under New Zealand regulations, the report said.

Mr Coker was one of two groups of four young tourists who were to undertake a tandem skydive jump where each passenger is paired with an experienced ''tandem master'' who is harnessed to them and who jumps out of the aircraft with them.

The first four, including Mr Coker, boarded the aircraft and the other four waited on the ground for their turn, and witnessed the accident.

The aircraft took off and reached 400 feet before the pilot appeared to lose control and the aircraft nosedived to the ground and burst into flames. All nine occupants were killed.

New Zealand law does not allow companies to be sued in the courts for negligence and has no criminal offence of corporate manslaughter.

Compensation is decided by the New Zealand Accident Compensation Corporation, the sole and compulsory provider of accident insurance in New Zealand, which determined the death of Bradley Coker merited compensation for the family of £2,744.

This compensation did not even cover the cost of the repatriation of Mr Coker's body to the United Kingdom.

His father has written to New Zealand PM John Key.

In the letter he said: ''Nothing you can do will bring back my son Bradley, who was killed in the prime of his life whilst enjoying a holiday in your country, and no amount of compensation could make up for his death.

''Bradley's death was completely avoidable and needless. The circumstances that led to his death are a shocking catalogue of behaviour that would be regarded as negligent in every civilised country in the world...and amply demonstrates the lack of proper regulation and control and the need for urgent and fundamental reform in the way this kind of activity in New Zealand is monitored, controlled and regulated.

''I urge you to act in the best interests of the thousands of young people who come to New Zealand every year to enjoy what you have to offer in such a beautiful country.

''Until you do act, the beauty of your country will continue to disguise a regulatory and legal culture that makes the public and visitors highly vulnerable and puts their lives in significant danger.

''Until action is taken to ensure the regulation, inspection and control of adventure sports, particularly involving aircraft, is radically tightened, I feel it my duty to advise people thinking of visiting New Zealand for adventure sport to think twice.''

Elizabeth Coker, Bradley's sister, and a UK lawyer, also said: ''When your brother travels to a Commonwealth country such as New Zealand, you naturally expect the safety standards and legal standards to match those of the UK or your home country, and this is not the case. You cannot sue for negligence in New Zealand and there is no criminal offence of corporate manslaughter. In our view, this has had the effect of lowering safety standards in New Zealand.''

A new civil aviation rule in New Zealand now requires skydiving and other adventure aviation operators to hold a CAA Operator Certificate.

The family of Mr Coker said it would do nothing to strengthen monitoring and control of the regulations, which might have saved Bradley's life.

Mr Coker was on holiday around Asia-Pacific, Australasia and South America in 2010 with his girlfriend, Hayley Denham.

The three other tourists who died were: Glen Bourke, 18, from Australia; Patrick Byrne, 26, from Ireland and Annika Kirsten Schmidt, 23, from Germany.

The five New Zealand crew who died were: pilot Chaminda Senadhira, 33, and skydiving instructors Adam Bennett, 47,; Christopher McDonald, 62; Rodney Miller, 55, and Michael Suter, 32.

An inquest in New Zealand into the death of Bradley Coker will be held in August.