The parents of a missing zoology graduate who disappeared in Africa six months ago have hit out at police, claiming they have done nothing to help.

Tim and Pauline Velten were shocked and dismayed when police officers searched their East Sussex home for their son Christian.

The officers explained missing persons were most often found in their own homes despite the fact Christian disappeared thousands of miles away from the family home in Burwash.

Mrs Velten said: "The first thing they did was search the house, which was a total insult to our intelligence.

"They said it was because most missing persons are found in their own houses. Can you believe it? I mean, how bloody ridiculous."

Mrs Velten called the police on August 16, five months after Christian, 28, went missing in Mali and almost a month after he had been due to fly back to the UK.

After the initial search, she said, several subsequent phone calls to the police went unreturned.

Two weeks later, Christian's return flight details were found by a friend. He was booked with Virgin.

Again, Mrs Velten said her calls to Sussex Police went unreturned.

Eventually the Foreign Office, through a contact in Lagos, established that he had neither caught nor cancelled his flight.

Christian, was on a five-month solo expedition retracing the steps of his hero, Mungo Park, to the source of the Niger.

He was making his way on foot from Gambia to Nigeria and his aim was to make a documentary.

The last time the Veltens spoke to their son was on March 23 when he rang them from Kita in Mali, west Africa.

Mrs Velten said: "He had said he wouldn't be in regular contact because of there being no communications. He was either going up river or was hiring a camel. So we didn't initially worry too much.

"But, after a couple of months, we realised he should have passed through Bamako in Mali, and then Timbuktu."

On May 19 they contacted the Foreign Office but an official search has still not been carried out.

Guided by the Veltens' initial belief Christian might be in Niger, the Foreign Office contacted the French Embassy there.

Over the next month, the British consular liaison network was informed in Nigeria, and then the French Embassy in Mali.

The British Embassy in Dakar, Senegal, was informed and is making inquiries, as is the liaison office in Bamako, Mali.

Christian's expedition was due to end on July 6. He had a flight home booked for July 22.

Sussex Police said an internal review and investigation was under way about its actions when Christian was reported missing.